metrics(hummock): add hummock version size metric

[hzxa21]

No description provided.

[codecov]

Codecov Report

Merging #2348 (f24d6d3) into main (0193870) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #2348      +/-   ##
==========================================
- Coverage   71.07%   71.05%   -0.02%     
==========================================
  Files         675      675              
  Lines       84502    84566      +64     
==========================================
+ Hits        60061    60091      +30     
- Misses      24441    24475      +34     

Flag	Coverage Δ
rust	71.05% <100.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/meta/src/hummock/metrics_utils.rs	96.32% <100.00%> (+0.08%)	⬆️
src/meta/src/rpc/metrics.rs	79.24% <100.00%> (+0.53%)	⬆️
src/meta/src/hummock/hummock_manager.rs	88.62% <0.00%> (-2.61%)	⬇️
src/meta/src/hummock/vacuum.rs	83.18% <0.00%> (-2.08%)	⬇️
src/common/src/types/ordered_float.rs	24.70% <0.00%> (-0.20%)	⬇️

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[soundOfDestiny]

easy! Since we have encoded_len()