rgw: s/std::map/boost::container::flat_map/ cls_bucket_list_ordered

rgw: s/std::map/boost::container::flat_map/ cls_bucket_list_ordered
(RGWRados and CLS).

Probably faster, allocating less.  Definitely not slower.

Examples from single-OSD vstart.sh cluster, Ceph built at -O2

BEFORE

[mbenjamin@lemon python]$ time  s3cmd -c s3cfg_userx ls  s3://DOCREQUEST_750/CSV/SUB1/ > /dev/null

real	4m48.991s
user	3m45.260s
sys	0m7.174s

(2nd run)

radosgw
Samples: 81K of event 'cycles:ppp', 4000 Hz, Event count (approx.): 3189324729
Overhead  Shared Object         Symbol
   7.06%  libtcmalloc.so.4.5.1  [.] tcmalloc::CentralFreeList::FetchFromOneSpans
   6.85%  libstdc++.so.6.0.25   [.] std::__ostream_insert<char, std::char_traits<char> >
   6.15%  librados.so.2.0.0     [.] ceph::buffer::v14_2_0::list::iterator_impl<true>::copy
   4.12%  librados.so.2.0.0     [.] ceph::buffer::v14_2_0::ptr::copy_out
   4.11%  libstdc++.so.6.0.25   [.] std::basic_streambuf<char, std::char_traits<char> >::xsputn
   3.49%  libc-2.27.so          [.] __memmove_avx_unaligned_erms
   3.33%  libtcmalloc.so.4.5.1  [.] tc_deletearray_aligned_nothrow
   3.04%  radosgw               [.] std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pa
   2.46%  radosgw               [.] std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::compare
   2.45%  libtcmalloc.so.4.5.1  [.] operator new[]
   2.39%  libstdc++.so.6.0.25   [.] std::ostream::sentry::sentry
   2.36%  radosgw               [.] std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pa
   2.07%  librados.so.2.0.0     [.] ceph::buffer::v14_2_0::list::iterator_impl<true>::advance
   1.94%  libc-2.27.so          [.] __memcmp_avx2_movbe
   1.93%  radosgw               [.] std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pa
   1.85%  librados.so.2.0.0     [.] ceph::buffer::v14_2_0::list::iterator_impl<true>::copy
   1.79%  radosgw               [.] rgw_bucket_dir::decode
   1.76%  libceph-common.so.0   [.] operator<<
   1.42%  radosgw               [.] ceph::decode
   1.35%  libstdc++.so.6.0.25   [.] std::_Rb_tree_insert_and_rebalance
   1.33%  libtcmalloc.so.4.5.1  [.] tcmalloc::CentralFreeList::ReleaseToSpans
   1.31%  librados.so.2.0.0     [.] std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::_M_mutate
   1.24%  [kernel]              [k] copy_user_enhanced_fast_string
For a higher level overview, try: perf top --sort comm,dso

osd

Samples: 23K of event 'cycles:ppp', 4000 Hz, Event count (approx.): 5059851086
Overhead  Shared Object         Symbol
   8.57%  libc-2.27.so          [.] vfprintf
   4.90%  ceph-osd              [.] ceph::logging::Log::_flush
   4.66%  libc-2.27.so          [.] _IO_default_xsputn
   3.49%  libtcmalloc.so.4.5.1  [.] operator new[]
   2.93%  ceph-osd              [.] StackStringBuf<4096ul>::xsputn
   2.70%  libstdc++.so.6.0.25   [.] std::__ostream_insert<char, std::char_traits<char> >
   2.11%  libpthread-2.27.so    [.] __pthread_mutex_unlock_usercnt
   1.91%  libc-2.27.so          [.] __memmove_avx_unaligned_erms
   1.75%  libstdc++.so.6.0.25   [.] std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::_M_insert_int<unsigned l
   1.64%  libc-2.27.so          [.] _itoa_word
   1.58%  libtcmalloc.so.4.5.1  [.] tc_deletearray_aligned_nothrow
   1.39%  libstdc++.so.6.0.25   [.] std::ostream::sentry::sentry
   1.33%  [kernel]              [k] stackleak_erase
   1.27%  [kernel]              [k] copy_user_enhanced_fast_string
   1.22%  libc-2.27.so          [.] __strlen_avx2
   1.15%  ceph-osd              [.] ceph::buffer::v14_2_0::list::append
   1.12%  libstdc++.so.6.0.25   [.] std::ostream::_M_insert<unsigned long>
   1.10%  ceph-osd              [.] ceph::buffer::v14_2_0::ptr::append
   1.04%  libpthread-2.27.so    [.] __pthread_mutex_lock
   1.01%  libc-2.27.so          [.] __tz_convert
   0.94%  [kernel]              [k] entry_SYSCALL_64
   0.94%  ceph-osd              [.] ceph::buffer::v14_2_0::list::iterator_impl<true>::copy
   0.93%  ceph-osd              [.] ceph::logging::Log::submit_entry
For a higher level overview, try: perf top --sort comm,dso

AFTER

[mbenjamin@lemon python]$ time  s3cmd -c s3cfg_userx ls  s3://DOCREQUEST_750/CSV/SUB1/ > /dev/null

real	4m51.488s
user	3m36.785s
sys	0m5.689s

(1st run)

radosgw

Samples: 52K of event 'cycles:ppp', 4000 Hz, Event count (approx.): 4426952205
Overhead  Shared Object         Symbol
   6.11%  librados.so.2.0.0     [.] ceph::buffer::v14_2_0::list::iterator_impl<true>::copy
   5.83%  libstdc++.so.6.0.25   [.] std::__ostream_insert<char, std::char_traits<char> >
   3.89%  radosgw               [.] rgw_bucket_dir::decode
   3.73%  radosgw               [.] rgw_bucket_dir_entry::rgw_bucket_dir_entry
   3.68%  librados.so.2.0.0     [.] ceph::buffer::v14_2_0::ptr::copy_out
   3.37%  libstdc++.so.6.0.25   [.] std::basic_streambuf<char, std::char_traits<char> >::xsputn
   3.14%  libtcmalloc.so.4.5.1  [.] tcmalloc::CentralFreeList::FetchFromOneSpans
   2.55%  libc-2.27.so          [.] __memmove_avx_unaligned_erms
   2.22%  libtcmalloc.so.4.5.1  [.] tc_deletearray_aligned_nothrow
   2.02%  libstdc++.so.6.0.25   [.] std::ostream::sentry::sentry
   1.79%  librados.so.2.0.0     [.] ceph::buffer::v14_2_0::list::iterator_impl<true>::advance
   1.77%  [kernel]              [k] n_tty_write
   1.74%  libc-2.27.so          [.] vfprintf
   1.71%  libtcmalloc.so.4.5.1  [.] operator new[]
   1.65%  librados.so.2.0.0     [.] ceph::buffer::v14_2_0::list::iterator_impl<true>::copy
   1.58%  radosgw               [.] ceph::decode
   1.38%  librados.so.2.0.0     [.] std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::_M_mutate
   1.22%  [kernel]              [k] stackleak_erase
   1.12%  libceph-common.so.0   [.] operator<<
   1.09%  libc-2.27.so          [.] _IO_default_xsputn
   1.06%  libc-2.27.so          [.] __memcmp_avx2_movbe
   1.04%  [kernel]              [k] copy_user_enhanced_fast_string
   0.93%  librados.so.2.0.0     [.] std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::_M_append
For a higher level overview, try: perf top --sort comm,dso

osd

Samples: 134K of event 'cycles:ppp', 4000 Hz, Event count (approx.): 26819176020
Overhead  Shared Object         Symbol
   8.82%  libc-2.27.so          [.] vfprintf
   6.88%  ceph-osd              [.] ceph::logging::Log::_flush
   4.80%  libc-2.27.so          [.] _IO_default_xsputn
   4.15%  libpthread-2.27.so    [.] __pthread_mutex_unlock_usercnt
   2.69%  ceph-osd              [.] StackStringBuf<4096ul>::xsputn
   2.54%  libstdc++.so.6.0.25   [.] std::__ostream_insert<char, std::char_traits<char> >
   2.40%  libtcmalloc.so.4.5.1  [.] operator new[]
   2.39%  libc-2.27.so          [.] __memmove_avx_unaligned_erms
   2.13%  libcls_rgw.so.1.0.0   [.] boost::container::dtl::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<ch
   1.61%  libtcmalloc.so.4.5.1  [.] tc_deletearray_aligned_nothrow
   1.54%  libc-2.27.so          [.] _itoa_word
   1.49%  libstdc++.so.6.0.25   [.] std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::_M_insert_int<unsigned l
   1.41%  libpthread-2.27.so    [.] __pthread_mutex_lock
   1.41%  ceph-osd              [.] ceph::logging::Log::submit_entry
   1.23%  libstdc++.so.6.0.25   [.] std::ostream::sentry::sentry
   1.19%  libc-2.27.so          [.] __tz_convert
   1.08%  libc-2.27.so          [.] __strlen_avx2
   1.08%  [kernel]              [k] stackleak_erase
   1.06%  libcls_rgw.so.1.0.0   [.] rgw_bucket_list
   1.02%  ceph-osd              [.] ceph::buffer::v14_2_0::list::append
   0.99%  ceph-osd              [.] ceph::buffer::v14_2_0::ptr::append
   0.96%  [kernel]              [k] copy_user_enhanced_fast_string
   0.93%  [kernel]              [k] entry_SYSCALL_64
For a higher level overview, try: perf top --sort comm,dso

Signed-off-by: Matt Benjamin <mbenjamin@redhat.com>