return delete marker for tombstone blob in on_fetch_data

[JacksonYao287]

this PR also:
1 add more detailed info in gc log
2 make gc data verification configurable.

[xiaoxichen]

lgtm except suggesting GCLOGD takes pg_id and shard_id

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 21.79487% with 61 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.24%. Comparing base (1746bcc) to head (28182c5).
⚠️ Report is 141 commits behind head on main.

Files with missing lines	Patch %	Lines
src/lib/homestore_backend/gc_manager.cpp	25.00%	43 Missing and 8 partials ⚠️
...ib/homestore_backend/replication_state_machine.cpp	0.00%	10 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #377      +/-   ##
==========================================
- Coverage   63.15%   60.24%   -2.92%     
==========================================
  Files          32       35       +3     
  Lines        1900     4593    +2693     
  Branches      204      578     +374     
==========================================
+ Hits         1200     2767    +1567     
- Misses        600     1533     +933     
- Partials      100      293     +193     

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[JacksonYao287]

lgtm except suggesting GCLOGD takes pg_id and shard_id

thanks for the input, I have made this change, ptal

[xiaoxichen]

please rebase and fix ut

[JacksonYao287]

please rebase and fix ut

code rebased and bug fixed. the new log of gc will be like this

 [gc_task_id=4, pg_id=1, shard_id=0x1000000000004] 5 valid blobs found in move_from_chunk=73

[Besroy]

LGTM

[JacksonYao287]

do we need set verify_blob = true?

https://github.com/eBay/HomeObject/pull/377/changes#diff-1e5351e846693d5e5d1cc75cd9685a6e1d5f29f5a1c8c4a1c438b9cfb594c8f7L37-L38

verify_blob will be true as default