refactor(internal/librarian/golang): refactor version functions in Go

[JoeWang1127]

Create functions to calculate client directory and versioned api path for Go package.

For #3617

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.06%. Comparing base (82168a3) to head (3339477).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4059      +/-   ##
==========================================
+ Coverage   82.04%   82.06%   +0.02%     
==========================================
  Files          78       78              
  Lines        6515     6519       +4     
==========================================
+ Hits         5345     5350       +5     
+ Misses        825      824       -1     
  Partials      345      345              

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[gemini-code-assist]

Code Review

This pull request refactors version-related functions into new helpers, improving code organization. However, it introduces or maintains several security vulnerabilities related to unvalidated configuration parameters. Specifically, the ClientDirectory value is used to construct filesystem paths and as a Go package name without proper validation, leading to potential Path Traversal and Code Injection vulnerabilities. I've provided suggestions to refine the refactoring to avoid redundant function calls and improve efficiency, along with test updates.