CI: Adding artifact attestations and fix warnings related to coverage upload

[ecoussoux-ansys]

This PR provides fixes for #1595 and #1596.

The warnings related to coverage upload reported in #1595 should be suppressed by fixing the directory / output file definitions for the html and xml reports in the "Create coverage files" steps of the linux unit and system tests jobs of the CI (both grpc and dotnet). That way, the coverage files will be properly discovered by the subsequent steps of the test jobs in charge of uploading the reports.

The artifact attestations and the associated release note comments are enabled using the option add-artifact-attestation-notes: true within the ansys/actions/release-github (see documentation on the action here).

Close #1595.
Close #1596.

[svandenb-dev]

LGTM

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.71%. Comparing base (518d344) to head (adcf176).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1601      +/-   ##
==========================================
+ Coverage   70.60%   70.71%   +0.11%     
==========================================
  Files         224      224              
  Lines       40286    40286              
==========================================
+ Hits        28442    28487      +45     
+ Misses      11844    11799      -45     

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[SMoraisAnsys]

Thanks for the contribution @ecoussoux-ansys
I think you are missing the attestation generation from the build jobs (to be added through input attest-provenance: true). Pay attention to the permission required when doing this change. I left a comment on the release job.