Refactoring rocksdb.rs

[yito88]

Describe your changes

• Use constants for keys
• Add helper functions
• Restore the merkle tree outside of read_last_block
  • It is restored by rebuilding after read_last_block in many cases
• Use batch for write_subspace_val and delete_subspace_val

Indicate on which release or other PRs this topic is based on

v0.33.0

Checklist before merging to draft

• I have added a changelog
• Git history is in acceptable state

[codecov]

Codecov Report

Attention: Patch coverage is 79.50192% with 107 lines in your changes are missing coverage. Please review.

Project coverage is 59.40%. Comparing base (97ec5b4) to head (fbba381).
Report is 4 commits behind head on main.

Files	Patch %	Lines
crates/storage/src/mockdb.rs	56.16%	64 Missing ⚠️
crates/apps/src/lib/node/ledger/storage/rocksdb.rs	88.31%	43 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #2938    +/-   ##
========================================
  Coverage   59.39%   59.40%            
========================================
  Files         298      298            
  Lines       92771    92478   -293     
========================================
- Hits        55104    54934   -170     
+ Misses      37667    37544   -123     

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[Fraccaman]

do u think we could also upgrade rocksdb dependency to 0.22.0? I started doing this is another PR but it was closed due to some other reasons. You can take a look here

[Fraccaman]

is this ready?