Update python-build-standalone workflow (#5390)

## Summary

After #5337, `fetch-download-metadata.py` fetches not just from
`python-build-standalone`, so updates the workflow to
`sync-python-releases.yml`.

Also includes `crates/uv-python/download-metadata.json` in `add-paths`.

---------

Co-authored-by: Zanie Blue <contact@zanie.dev>

.github/workflows/sync-python-releases.yml

@@ -0,0 +1,39 @@
+# Sync Python releases and create a pull request.
+#
+# Based on: https://github.com/astral-sh/rye/blob/57b7c089e494138aae29a130afb2e17f447970bf/.github/workflows/sync-python-releases.yml
+name: "Sync Python downloads"
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: "0 0 * * *"
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  sync:
+    if: github.repository == 'astral-sh/uv'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: hynek/setup-cached-uv@v1
+      - name: Sync Python Releases
+        run: |
+          uv run --isolated -- fetch-download-metadata.py
+          uv run --isolated -- template-download-metadata.py
+        working-directory: ./crates/uv-python
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: "Create Pull Request"
+        uses: peter-evans/create-pull-request@v6
+        with:
+          commit-message: "Sync latest Python releases"
+          add-paths: |
+            crates/uv-python/download-metadata.json
+            crates/uv-python/src/downloads.inc"
+          branch: "sync-python-releases"
+          title: "Sync latest Python releases"
+          body: "Automated update for Python releases."
+          base: "main"