update codecov/codecov-action v3 -> v4

[Bastian-Krause]

Description

GitHub emits warnings like:

The following actions use a deprecated Node.js version and will be forced to run on node20: codecov/codecov-action@v3. For more info:
https://github.blog/changelog/2024-03-07-github-actions-all-actions-will-run-on-node20-instead-of-node16-by-default/

The codecov upload hasn't worked reliably in a while. This should fix it.

[Bastian-Krause]

Rebased on latest master.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 56.8%. Comparing base (5e4ab58) to head (b6c9e4e).
Report is 73 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #1508     +/-   ##
========================================
- Coverage    61.8%   56.8%   -5.1%     
========================================
  Files         166     168      +2     
  Lines       12305   13000    +695     
========================================
- Hits         7605    7384    -221     
- Misses       4700    5616    +916     

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[Bastian-Krause]

Sending SIGTERM to the coordinator/exporter processes results in a "Terminated" message. This typically comes from the shell (or OS) when a process doesn't handle SIGTERM explicitly. The OS kills the process immediately, and this prevents Python from running cleanup tasks, such as saving coverage data or executing other signal handlers.

Simply using SIGINT instead does not work reliably. This needs more investigation. Until that's fixed, let's rather live with the coverage drop than having no coverage tracking at all.

[Bastian-Krause]

Dropped the exporter/coordinator coverage collection fix for now.