Auto merge of #29639 - mrobinson:reorganize-wpt-python, r=mukilan

Reorganize Servo's WPT Python scripts

This change moves all of Servo's WPT Python support scripts into one directory as they were previously scattered throughout the directory structure. This should allow more code reuse and make it easier to understand how everything fits together.

The changes:

- `tests/wpt/update` → `python/wpt/importer`
- `etc/ci/upstream-wpt-changes/wptupstreamer` → `python/wpt/exporter`
- `etc/ci/upstream-wpt-changes/test.py` → `python/wpt/test.py`
- `etc/ci/upstream-wpt-changes/tests` → `python/wpt/tests`
- `tests/wpt/servowpt.py` → - `python/wpt/update.py` - `python/wpt/run.py`
- `tests/wpt/manifestupdate.py` → `python/wpt/manifestupdate.py`

This change also removes
 - The ability to run the `update-wpt` and `test-wpt` commands without using `mach`. These didn't work very well, because it was difficult to get all of the wptrunner and mach dependencies installed outside of the Python virtualenv. It's simpler if they are always run through `mach`.
- The old WPT change sync / upstreaming script that was no longer used. This allows this code to pass `test-tidy` now.

<!-- Please describe your changes on the following line: -->

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] There are tests for these changes

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<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

.github/workflows/pull-request-wpt-export.yml

@@ -32,9 +32,9 @@ jobs:
           # See https://github.com/actions/checkout/issues/162.
           token: ${{ secrets.WPT_SYNC_TOKEN }}
       - name: Install requirements
-        run: pip install -r servo/etc/ci/upstream-wpt-changes/requirements.txt
+        run: pip install -r servo/python/wpt/requirements.txt
       - name: Process pull request
-        run: servo/etc/ci/upstream-wpt-changes/upstream-wpt-changes.py
+        run: servo/python/wpt/upstream.py
         env:
           GITHUB_CONTEXT: ${{ toJson(github) }}
-          WPT_SYNC_TOKEN: ${{ secrets.WPT_SYNC_TOKEN }}
+          WPT_SYNC_TOKEN: ${{ secrets.WPT_SYNC_TOKEN }}

.github/workflows/test-export-wpt-changes.yml

@@ -2,7 +2,7 @@ name: WPT exporter test
 on:
   pull_request:
     branches: ["**"]
-    paths: ["etc/ci/upstream-wpt-changes/**"]
+    paths: ["python/wpt/exporter/**"]
 
 jobs:
   test:
@@ -12,7 +12,7 @@ jobs:
       - uses: actions/checkout@v3
       - name: Install dependencies
         run: |
-          python3 -m pip install --upgrade -r etc/ci/upstream-wpt-changes/requirements-dev.txt
+          python3 -m pip install --upgrade -r python/wpt/requirements-dev.txt
       - name: Running tests
         run: |
-          python3 etc/ci/upstream-wpt-changes/test.py
+          python3 python/wpt/test.py