chore(ci): switch to cargo-llvm-cov for code coverage

[orhun]

Description

Switching to cargo-llvm-cov due to the recent bugs with cargo-tarpaulin.

How Has This Been Tested?

CI

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: CI

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

All modified and coverable lines are covered by tests ✅

Project coverage is 82.11%. Comparing base (fa5105d) to head (7f84c70).

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Additional details and impacted files

@@             Coverage Diff             @@
##           master     #260       +/-   ##
===========================================
+ Coverage   70.09%   82.11%   +12.02%     
===========================================
  Files          11       11               
  Lines         632     1219      +587     
===========================================
+ Hits          443     1001      +558     
- Misses        189      218       +29     

Flag	Coverage Δ
unit-tests	82.11% <ø> (+12.02%)	⬆️

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