Install with package manager

Description:

Currently, if we use poetry, we have to write two steps:

      - name: Install poetry
        run: pipx install poetry

      - name: Set up Python
        uses: actions/setup-python@v4
        with:
          python-version: ...
          cache: poetry

I hope this can be easier:

      - name: Set up Python
        uses: actions/setup-python@v4
        with:
          python-version: ...
          package-manager: poetry@{version}
          cache: poetry

Start by reviewing the actions/setup-python@v4 entry point and how its current cache: poetry setup handles the separate Poetry installation step. Define the package-manager input and its version behavior, then verify that a workflow can install the requested Poetry version through the single setup step while preserving dependency caching.