common: cache pthread names

common: cache pthread names

This provides common ceph entrypoints for the pthread_[gs]name functions which
will also cache a thread_local copy. This also removes the pthread_t parameter
which precipitated the bug i50743.

Obviously, the overall goal here is to avoid system calls.

See-also: https://tracker.ceph.com/issues/50743
Fixes: 0be8d01c9ddde0d7d24edd34dc75f6cfc861b5ba
Fixes: https://tracker.ceph.com/issues/68691
Signed-off-by: Patrick Donnelly <pdonnell@ibm.com>
(cherry picked from commit 7de5af59c2741b4203cc17f619ca53096c97b8ff)

Conflicts:
	src/ceph_nvmeof_monitor_client.cc: not present
	src/mds/Beacon.cc: trivial