分库分表：Inserter 支持分库分表

[codecov[bot]]

Codecov Report

Merging #200 (1ac5d40) into dev (d75d819) will decrease coverage by 0.56%. The diff coverage is 77.02%.

@@            Coverage Diff             @@
##              dev     #200      +/-   ##
==========================================
- Coverage   85.93%   85.37%   -0.56%     
==========================================
  Files          45       47       +2     
  Lines        3313     3535     +222     
==========================================
+ Hits         2847     3018     +171     
- Misses        374      410      +36     
- Partials       92      107      +15     

Impacted Files	Coverage Δ
internal/model/model.go	83.80% <ø> (ø)
sharding_result.go	66.66% <66.66%> (ø)
sharding_insert.go	77.77% <77.77%> (ø)

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[flycash]

用 ekit 的 dev 分支中的 TreeMap 替换了现在的写法