Supports sharding store for LevelDB

[boqiu]

This change is 

[codecov]

Codecov Report

❌ Patch coverage is 53.33333% with 105 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.41%. Comparing base (5b84241) to head (6241d95).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
store/leveldb/store_shard.go	48.74%	86 Missing and 16 partials ⚠️
store/leveldb/store_rw.go	88.23%	1 Missing and 1 partial ⚠️
store/leveldb/store.go	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #73      +/-   ##
==========================================
- Coverage   77.64%   74.41%   -3.24%     
==========================================
  Files          20       21       +1     
  Lines        1360     1278      -82     
==========================================
- Hits         1056      951     -105     
- Misses        260      268       +8     
- Partials       44       59      +15     

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[wanliqun]

@wanliqun reviewed 12 of 12 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @boqiu)