Merge PR #21825 into master

* refs/pull/21825/head:
	os/bluestore: rename new bitmap allocator class to BitmapAllocator.
	os/bluestore: perform allocations aligned with min_length  in new bitmap allocator
	test/objectstore/unitetest_fastbmap_allocator: replace ASSERT_TRUE with
	os/bluestore: respect min_length as allocation granularity for new
	os/bluestore: cosmetic new allocator internal method rename.
	os/bluestore: properly respect min_length when analysing partially free
	os/bluestore: cosmetic cleanup in new bitmap allocator.
	os/bluestore: more verbose logging in new bitmap allocator
	os/bluestore: default to bitmap allocator for bluestore/bluefs
	os/bluestore: remove original bitmap allocator
	os/bluestore: align BitMap allocator's init_rm_free/init_add_free parameters with min_alloc_size
	os/bluestore: fix improper access to a BitmapFastAllocator::last_pos
	test/allocator: move bluestore allocator's benchmarks to a standalone UT
	os/bluestore: add new bitmap allocator
	test/allocator: get rid off bitmap allocator specifics and introduce new
	test/fio: dump mempool on job completion

Reviewed-by: Varada Kari <varadaraja.kari@flipkart.com>