Add invalidate-cache flag

[drew2a]

This feature was requested by @xoriole in #6923

1. I forked and changed the restore-virtualenv action syphar/restore-virtualenv@091a22a
2. I added invalidate-cache flag to the venv action

So, if you need to "refresh" the cache, you can run the pyenv action with invalidate-cache: true just once and the cache for this branch will be recreated.

      - name: Create python environment
        uses: ./.github/actions/pyenv
        with:
          python-version: ${{inputs.python-version}}
          requirements: requirements-test.txt
          invalidate-cache: true

Ref:

• https://docs.github.com/en/actions/creating-actions/creating-a-javascript-action