Fix and Improve `fix pg size & shard identical layout`

[Hooper9973]

Bug Fixes:

• Resolved issues in create_shard and seal_shard functions to ensure correct shard management. Enhancements:
• Added validation to prevent creation of placement groups with sizes smaller than the chunk size. Test Improvements:
• pg test:
  • Added tests to verify that creating a placement group with a size smaller than the chunk size results in failure.
• shard test:
  • Created shard but shard size is larger than pg space left which should be failed.
  • Verified that successfully created shards have identical virtual chunk layouts.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 64.70588% with 6 lines in your changes missing coverage. Please review.

Project coverage is 65.30%. Comparing base (1746bcc) to head (6e5e52e). Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
...ib/homestore_backend/replication_state_machine.cpp	0.00%	2 Missing and 1 partial :warning:
src/lib/homestore_backend/heap_chunk_selector.cpp	50.00%	1 Missing and 1 partial :warning:
src/lib/homestore_backend/hs_shard_manager.cpp	85.71%	1 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #235 +/- ## ========================================== + Coverage 63.15% 65.30% +2.14% ========================================== Files 32 32 Lines 1900 1977 +77 Branches 204 213 +9 ========================================== + Hits 1200 1291 +91 + Misses 600 578 -22 - Partials 100 108 +8 ```

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