fix(changelog): update the commit processing order

[orhun]

Description

This PR updates the order of commit processing from:

1. Split commits
2. Process commits

To:

1. Process commits
2. Split commits (and process splitted commits)

Motivation and Context

closes #555

How Has This Been Tested?

cargo test

Types of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (no code change)
• Refactor (refactoring production code)
• Other

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly.
• I have formatted the code with rustfmt.
• I checked the lints with clippy.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 78.57143% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 41.27%. Comparing base (9eb3d65) to head (1f6c00c).
⚠️ Report is 376 commits behind head on main.

Files with missing lines	Patch %	Lines
git-cliff-core/src/changelog.rs	75.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #556      +/-   ##
==========================================
+ Coverage   41.07%   41.27%   +0.21%     
==========================================
  Files          15       15              
  Lines        1069     1071       +2     
==========================================
+ Hits          439      442       +3     
+ Misses        630      629       -1     

Flag	Coverage Δ
unit-tests	41.27% <78.58%> (+0.21%)	⬆️

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