.github/workflows/ci.yml: improvements

[tarasmadan]

Is your feature request related to a problem? Please describe.
Arc v2 based ci runners configuration may be better.

Describe the solution you'd like

1. GCP autoscaling doesn't work. Let's monitor Docker Container Action Jobs failing to schedule on autoscaled cluster actions/runner-container-hooks#140 progress.
2. The runners scale down to 0. Setting minRunners to 4-6-8 we can save 30 seconds for every job.
3. Force-push creates new testing request. We don't cancel already started requests for that PR. It makes sense to cancel them. GH documentation knows how to do it.
4. [Done, .github/workflows/ci.yml: require min 31 core per test job #4537 ] We don't limit the runners count. Having more runners than instances may be the source of timeout-error. It makes sense to fix maxRunners.
5. The caching doesn't work. Effective cache size is 0.
6. [Done, it seems to be a spot VMs usage side effect] Some jobs finish with 130 error.
7. [Done, .github/workflows/ci.yml: workaround codecov limitation to detect environment #4558] CodeCov requires additional configuration. It doesn't properly detect "Github Actions" environment.

[tarasmadan]

#4537 surprisingly limited amount of runners/machine to 1.

[tarasmadan]

Removed spot machines pool. Added normal machines.
As a result, I don't see the jobs to fail with 130 error.
With high probability 130 error was a preemption side affect.
To use spot VMs, ARC has to restart the job in case of error.
We can modify ci.yml to restart jobs, but I don't want to pollute the ci.yml file.

[tarasmadan]

One more problem - codecov detects "Local" environment instead of "Github Actions".
Normal log "['info'] Detected GitHub Actions as the CI provider."
Current log "['info'] Detected Local as the CI provider."

[tarasmadan]

#4558 to workaround codecov problem.