refactor(ChangelogFormat): refactor get_metadata_from_file for better readability and type

[bearomorphism]

… readability and better type

Description

Checklist

• [ ] I have read the contributing guidelines

Code Changes

• [ ] Add test cases to all the changes you introduce
• [ ] Run poetry all locally to ensure this change passes linter check and tests
• [ ] Manually test the changes:
  • [ ] Verify the feature/bug fix works as expected in real-world scenarios
  • [ ] Test edge cases and error conditions
  • [ ] Ensure backward compatibility is maintained
  • [ ] Document any manual testing steps performed
• [ ] Update the documentation for the changes

Documentation Changes

• [ ] Run poetry doc locally to ensure the documentation pages renders correctly
• [ ] Check and fix any broken links (internal or external) in the documentation

When running poetry doc, any broken internal documentation links will be reported in the console output like this:

INFO    -  Doc file 'config.md' contains a link 'commands/bump.md#-post_bump_hooks', but the doc 'commands/bump.md' does not contain an anchor '#-post_bump_hooks'.

Expected Behavior

Steps to Test This Pull Request

Additional Context

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 98.25%. Comparing base (120d514) to head (edf22a8). :warning: Report is 808 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1596      +/-   ##
==========================================
+ Coverage   97.33%   98.25%   +0.91%     
==========================================
  Files          42       58      +16     
  Lines        2104     2692     +588     
==========================================
+ Hits         2048     2645     +597     
+ Misses         56       47       -9     

Flag	Coverage Δ
unittests	98.25% <100.00%> (+0.91%)	:arrow_up:

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