feat: file cache skeleton

[MrCroxx]

What changes were proposed in this pull request?

Introduce file cache skeleton.

Which issues is this PR related to?

#171

[codecov]

Codecov Report

Merging #173 (26a38dd) into main (4bc46a1) will increase coverage by 0.14%.
The diff coverage is 90.05%.

@@            Coverage Diff             @@
##             main     #173      +/-   ##
==========================================
+ Coverage   83.87%   84.01%   +0.14%     
==========================================
  Files          90       90              
  Lines        8850     9028     +178     
==========================================
+ Hits         7423     7585     +162     
- Misses       1427     1443      +16     

Impacted Files	Coverage Δ
storage/src/file_cache/error.rs	0.00% <ø> (ø)
storage/src/file_cache/buffer.rs	76.72% <45.45%> (-0.98%)	⬇️
storage/src/file_cache/file.rs	93.25% <92.94%> (-6.75%)	⬇️
wheel/src/worker/sstable_uploader.rs	76.85% <0.00%> (-1.66%)	⬇️
wheel/src/worker/raft.rs	94.45% <0.00%> (-0.17%)	⬇️
storage/src/raft_log_store/store.rs	92.70% <0.00%> (+0.23%)	⬆️
wheel/src/lib.rs	91.02% <0.00%> (+0.42%)	⬆️
wheel/src/components/raft_log_store.rs	67.72% <0.00%> (+0.63%)	⬆️

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