chore: add cargo machete and remove unused dependencies

[gruebel]

Changes

• removed unused dependencies
• added cargo machete job to CI to make sure no unused dependencies are left over
• also updated actions/checkout GHA to the latest version v4

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: cijothomas / name: Cijo Thomas (12b06be)
• ✅ login: gruebel / name: Anton Grübel (31ec233)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.6%. Comparing base (56a6f45) to head (12b06be).
Report is 37 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #119     +/-   ##
=======================================
+ Coverage   52.3%   58.6%   +6.3%     
=======================================
  Files         38      39      +1     
  Lines       4967    5774    +807     
=======================================
+ Hits        2598    3387    +789     
- Misses      2369    2387     +18     

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