ci(coverage): restore builds on master, fix Codecov coverage report and adds test analytics (fix #1606)

[noirbizarre]

Description

Run tests on the master branch (@Lee-W @woile not sure why it was not the case, so I'll let you check if this is OK for you).
This should restore the Codecov master report and so provide a viable coverage patch diff on pull requests.

It also adds support for Codecov test analytics as it is free for OSS projects and provides a few interesting insights (detailed test duration over time, flaky tests detection) as well as improved feedback on failure.

Coverage report now runs for all platforms (to properly track total number of runs by test
as well as tests or code only running on a given platform).

Redundant default parameters have been removed.

Checklist

• I have read the contributing guidelines

Code Changes

No code change.

junit.xml output added to poetry cover command (and resulting artifact added to .gitignore)

Documentation Changes

No documentation change

Expected Behavior

Up-to-date coverage report, working patch-diff on pull request.
Benefit of new Codecov features.
The test suite runs on master so:

• we detect post-merge failures early
• contributors know that the build is currently 🟢 and in case of failure on their branch, it's most probably their branch
• the coverage badge is updated with the current coverage

Steps to Test This Pull Request

Fixes #1606

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.92%. Comparing base (120d514) to head (b92d3ea).
⚠️ Report is 901 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1750      +/-   ##
==========================================
+ Coverage   97.33%   97.92%   +0.58%     
==========================================
  Files          42       60      +18     
  Lines        2104     2604     +500     
==========================================
+ Hits         2048     2550     +502     
+ Misses         56       54       -2     

Flag	Coverage Δ
unittests	?

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☔ View full report in Codecov by Sentry.
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🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Lee-W]

I believe the reason is that we never push to the master branch; it should be checked before merging. BUT, we do not enforce the branch up to date before merging (and I'm -0 to adding that constraint). So I'm happy we adding this :)

[bearomorphism]

Thanks!

[woile]

nice!