Merge PR #53503 into main

* refs/pull/53503/head:
	qa: add tests for `mds last-seen` command
	doc/cephfs: add documentation for `mds last-seen`
	PendingReleaseNotes: add note on last-seen command
	mon/MDSMonitor: add command to lookup when mds was last seen
	mon/MDSMonitor: set birth time on FSMap during encode
	pybind/mgr/dashboard: show context diff for openapi check

Reviewed-by: Venky Shankar <vshankar@redhat.com>

diff --cc PendingReleaseNotes
Simple merge

diff --cc qa/tasks/cephfs/test_admin.py
Simple merge

diff --cc src/mds/FSMap.cc
Simple merge

diff --cc src/mon/MonCommands.h
Simple merge

diff --cc src/pybind/mgr/dashboard/openapi.yaml
Simple merge