Consider more cost effective option for running python action check

[ArBridgeman]

Summary

The .github/workflows/test-python-environment.yml is executed for every CI run, provided that the manual-environment is approved. This means that for any PR in the toolbox that this needs to be run for it to be merged.

However, unlike unit & integration tests, which rely on the exasol-toolbox code, the .github/workflows/test-python-environment.yml is only testing if ./.github/actions/python-environment works for different runners, and this would NOT depend on the code in the exasol/toolbox. Thus, we could consider for cost reduction benefits to execute this differently:

• periodically with the CI -> if there's a failure, alert a channel?
• in a PR & require it, whenever a file in .github/actions/python-environment has been changed.