Implement ReplicationStateMachine::write_snapshot_data

[koujl]

• Implement ReplicationStateMachine::write_snapshot_data() and SnapshotReceiveHandler logic
• Extract local_create_pg, local_create_shard and local_add_blob_info for follower data creation

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 20.40816% with 195 lines in your changes missing coverage. Please review.

Please upload report for BASE (baseline_resync@7b9819d). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...lib/homestore_backend/snapshot_receive_handler.cpp	0.00%	133 Missing ⚠️
...ib/homestore_backend/replication_state_machine.cpp	0.00%	53 Missing ⚠️
src/lib/homestore_backend/hs_blob_manager.cpp	76.92%	4 Missing and 2 partials ⚠️
src/lib/homestore_backend/hs_pg_manager.cpp	87.50%	1 Missing and 1 partial ⚠️
src/lib/homestore_backend/hs_shard_manager.cpp	94.11%	1 Missing ⚠️

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Additional details and impacted files

@@                Coverage Diff                 @@
##             baseline_resync     #227   +/-   ##
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  Coverage                   ?   51.53%           
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  Files                      ?       33           
  Lines                      ?     2053           
  Branches                   ?      236           
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  Hits                       ?     1058           
  Misses                     ?      906           
  Partials                   ?       89           

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[yamingk]

I didn't see this is being used expect for the check to reuse this handler instance. Can we remove this field and the check and always reuse this handler instance?

[koujl]

The follower may receive a new snapshot transmission request if the leader crashes or if the previous snapshot transmission times out. The current LSN is necessary for the follower to recognize such cases and discard the current handler instance.

[koujl]

Added several TODOs as reminders for suggestions mentioned in the comments.

Further optimization & refactor will be posted within next PR.

[JacksonYao287]

LGTM