[CI] Update code coverage workflow

[wysiwys]

This PR updates the coverage.yml workflow in CI to replace -Zprofile (which is no longer available) with -Cinstrument-coverage and the options it needs for doctests. It also replaces actions-rs/grcov with grcov installed via cargo.

[franziskuskiefer]

lgtm

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 44.65%. Comparing base (816b9f5) to head (0081b11).
Report is 67 commits behind head on main.

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Additional details and impacted files

@@             Coverage Diff             @@
##             main      #74       +/-   ##
===========================================
- Coverage   60.73%   44.65%   -16.08%     
===========================================
  Files          18       15        -3     
  Lines        1640     3630     +1990     
===========================================
+ Hits          996     1621      +625     
- Misses        644     2009     +1365     

see 18 files with indirect coverage changes

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