Merge pull request #52267 from xxhdx1985126/wip-crimson-pg-snapmapper-obj

crimson/osd: put snapmapper's key-value pairs into dedicated objs

Reviewed-by: Samuel Just <sjust@redhat.com>
Reviewed-by: Matan Breizman <mbreizma@redhat.com>

diff --cc src/crimson/os/seastore/seastore.cc
Simple merge

diff --cc src/crimson/os/seastore/seastore.h
Simple merge

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

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