cl/convert:mod instead OutputDir in Package

[luoliwoshang]

Package修改为接受gopmod.Module替代当前的OutputDir在Package中的耦合,目前Package应该负责的是gogen.Package的构建，而之前的OutputDir会导致Package需要额外关心怎么去加载这个Mod以及Catch一些Error，但实际上这个原子能力应该只去关心怎么使用这个go.Mod带来的能力，而修改为gopmod.Module，调用者也可以更灵活的创建模块。

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The Package should currently be responsible for building gogen.Package, while the previous OutputDir would require Package to additionally handle how to load this Mod and catch some errors. In fact, this atomic capability should only focus on how to use the capabilities provided by go.Mod. By changing to gopmod.Module, the caller can also more flexibly create the module.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.92%. Comparing base (168c99c) to head (69f8c6c).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #346      +/-   ##
==========================================
+ Coverage   80.84%   80.92%   +0.08%     
==========================================
  Files          30       30              
  Lines        3638     3638              
==========================================
+ Hits         2941     2944       +3     
+ Misses        665      663       -2     
+ Partials       32       31       -1     

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