Merge pull request #57828 from xxhdx1985126/wip-seastore-btree-better-ut-asserts

crimson/os/seastore/btree: improve lba pointer related UT checks

Reviewed-by: Yingxin Cheng <yingxin.cheng@intel.com>

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