Patch metadata-validation Github action: use external python

The upstream hardware-metadata-validation action presently fails to install
Python dependencies with a permissions error for the pip cache directory. Until
it's fixed upstream, patch the action to use Github's `setup-python` and a
virtualenv to obtain a functioning Python enviroment.

.github/workflows/hardware-metadata-validation.yml

@@ -21,6 +21,18 @@ jobs:
       image: docker.io/zmkfirmware/zmk-dev-arm:3.5
     steps:
       - uses: actions/checkout@v4
+      - name: Take ownership of /github/home (temporary patch)
+        run: chown -R $(whoami) /github/home
+      - name: Install python environment (temporary patch)
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+      - name: Setup Python virtual environment (temporary patch)
+        run: |
+          python3 -m venv /tmp/venv
+          . /tmp/venv/bin/activate
+          echo VIRTUAL_ENV="$VIRTUAL_ENV" >> $GITHUB_ENV
+          echo PATH="$PATH" >> $GITHUB_ENV
       - name: Install dependencies
         run: pip install -r app/scripts/requirements.txt
       - name: West init