support manual trigger snapshot creation function

[Besroy]

Add manual snapshot creation API for log truncation control.
This implements option 1 from #835 with two capabilities:

1. Update truncation upper limit: Allows truncating logs up to a specified threshold when the in-memory truncation_upper_limit is zero (e.g., after restart).
2. Trigger snapshot via NuRaft API: Leverages NuRaft's snapshot creation API with two modes:
   • Async mode (recommended with ongoing traffic): Schedules snapshot creation for the next available committed log
   • Sync mode (for idle periods): Triggers snapshot creation immediately
     NuRaft handles race conditions internally so we don't need to do more (e.g., rejecting concurrent snapshot requests and using distance checks and flags to prevent concurrency issues)

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 9.52381% with 19 lines in your changes missing coverage. Please review.
✅ Project coverage is 49.56%. Comparing base (1a0cef8) to head (e1af472).
⚠️ Report is 295 commits behind head on master.

Files with missing lines	Patch %	Lines
src/lib/replication/repl_dev/raft_repl_dev.cpp	14.28%	11 Missing and 1 partial ⚠️
src/lib/replication/service/raft_repl_service.cpp	0.00%	5 Missing ⚠️
src/lib/replication/repl_dev/solo_repl_dev.h	0.00%	1 Missing ⚠️
src/lib/replication/service/generic_repl_svc.cpp	0.00%	1 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #840      +/-   ##
==========================================
- Coverage   56.51%   49.56%   -6.95%     
==========================================
  Files         108      110       +2     
  Lines       10300    11338    +1038     
  Branches     1402     5344    +3942     
==========================================
- Hits         5821     5620     -201     
+ Misses       3894     2101    -1793     
- Partials      585     3617    +3032     

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[Besroy]

No need, found the root cause is we didn't save receiving_snapshot_ in srv_state