feat: impl sst uploader and fix bugs

[MrCroxx]

• Implementate background sstable uploader.
• Wrap VersionManager with a tokio::sync::RwLock.
• Fix a wrong mut borrowing of memtable.
• Fix filtering sstable in VersionManager, use user key rather than full key.
• Temporarily add some commented println!s for debugging.

Ref: #44

[codecov-commenter]

Codecov Report

Merging #56 (f335d88) into main (0cfe294) will increase coverage by 1.11%. The diff coverage is 90.75%.

@@            Coverage Diff             @@
##             main      #56      +/-   ##
==========================================
+ Coverage   91.26%   92.38%   +1.11%     
==========================================
  Files          29       30       +1     
  Lines        3056     3164     +108     
==========================================
+ Hits         2789     2923     +134     
+ Misses        267      241      -26     

Impacted Files	Coverage Δ
storage/src/lsm_tree/utils/coding.rs	89.78% <ø> (+0.72%)	:arrow_up:
storage/src/lsm_tree/components/sstable.rs	94.00% <69.23%> (-2.13%)	:arrow_down:
storage/src/lsm_tree/manifest/version.rs	94.15% <78.78%> (-0.70%)	:arrow_down:
storage/src/lsm_tree/uploader.rs	95.16% <95.16%> (ø)
storage/src/lsm_tree/object_store_lsm_tree.rs	92.95% <96.77%> (ø)
storage/src/lsm_tree/components/memtable.rs	100.00% <100.00%> (ø)
storage/src/lsm_tree/iterator/user_key_iterator.rs	99.40% <0.00%> (+0.89%)	:arrow_up:
... and 2 more

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