Merge pull request #53151 from xxhdx1985126/wip-crimson-backfill-fixes

crimson/osd/backfill_state: fixes two corner cases in backfilling

Reviewed-by: Radosław Zarzyński <rzarzyns@redhat.com>

diff --cc src/crimson/osd/backfill_state.cc
Simple merge

diff --cc src/crimson/osd/pg_recovery.h
Simple merge

diff --cc src/crimson/osd/recovery_backend.cc
Simple merge