Merge pull request #46417 from xxhdx1985126/wip-gc-parallel-live_extent_retrieval

crimson/os/seastore/segment_cleaner: parallel live extents retrieval

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

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

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

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