Coveralls fixes

[lslezak]

Problem

• The Coveralls reporting step in the GitHub Actions got stuck (example job)
• And because the default timeout is 6 hours then the CI was stuck for 6 hours
• The number of the assigned Action runners is limited so after reaching the limit new CI actions were not started and were waiting until some previous job is finished.

Debugging

• At first I noticed an error in the Coveralls output:
  ⚠️ git log -1 --pretty=format:'%H%n%aN%n%aE%n%cN%n%cE%n%s' (return code 128)
  see https://github.com/agama-project/agama/actions/runs/15023225072/job/42217441468#step:14:166
• Running this command in a separate step showed that it was failing because of a different file owner:
  fatal: detected dubious ownership in repository at '/__w/agama/agama'
  see https://github.com/agama-project/agama/actions/runs/15020310724/job/42207691974#step:9:9
• But even after adding that config command it got still stuck
• After enabling the Coveralls steps in the web frontend again I noticed that it works fine without any problem so I tested moving the Coveralls step outside the container and it worked.
• Very likely there is some incompatibility in the Coveralls action and it does not work well when running inside a container with openSUSE Tumbleweed (Different git CLI tool? Different glibc, nodejs or something else?)

Solution

• Enable back the code coverage reporting in the web frontend
• Configure git so a different owner is OK (this was not the root of the problem in the end but this could cause troubles elsewhere later so I'm keeping this change anyway.)
• Run the coverage actions outside container, run them in the Ubuntu host directly
  (That's a bit tricky, if a job runs in a container then all steps run in the container, you cannot run a command outside the container. The workaround is to define a dependent job which runs outside the container and pass the coverage data as an artifact which is uploaded/downloaded.)
• Decrease the timeout, explicitly set 1 hour for CI and 20 minutes for Coveralls to not block for too long if the job gets stuck for whatever reason.
• Limit the permissions as suggested by the GitHub scanner to only read the repository content.

Testing

• Works fine, see the green marks for this pull request, the Coveralls reports were correctly sent.

[joseivanlopez]

LGTM