Combine all script tests into test-scripts

Remove:
    - tidy self test support from `./mach test`
    - `./mach test-idl`

Adds a `./mach test-scripts` command that is responsible for running all
Python script tests. Run this during the CI to catch regressions in
changes to scripts. The WebIDL tests are still *very* slow and there are
from Gecko, so only run them when "-a" is passed meaning all tests.

.github/workflows/linux.yml

@@ -75,6 +75,8 @@ jobs:
         run: python3 ./mach build --release --with-${{ env.LAYOUT }}
       - name: Smoketest
         run: xvfb-run python3 ./mach smoketest
+      - name: Script tests
+        run: ./mach test-scripts
       - name: Unit tests
         if: ${{ inputs.unit-tests }}
         run: python3 ./mach test-unit --release --with-${{ env.LAYOUT }}

.github/workflows/mac.yml

@@ -63,6 +63,8 @@ jobs:
           python3 ./mach build --release --with-${{ env.LAYOUT }}
       - name: Smoketest
         run: python3 ./mach smoketest
+      - name: Script tests
+        run: ./mach test-scripts
       - name: Unit tests
         if: ${{ inputs.unit-tests }}
         run: python3 ./mach test-unit --release --with-${{ env.LAYOUT }}

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

@@ -32,7 +32,7 @@ jobs:
           # See https://github.com/actions/checkout/issues/162.
           token: ${{ secrets.WPT_SYNC_TOKEN }}
       - name: Install requirements
-        run: pip install -r servo/python/wpt/requirements.txt
+        run: pip install -r servo/python/requirements.txt
       - name: Process pull request
         run: servo/python/wpt/export.py
         env:

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

@@ -1,18 +0,0 @@
-name: WPT exporter test
-on:
-  pull_request:
-    branches: ["**"]
-    paths: ["python/wpt/exporter/**"]
-
-jobs:
-  test:
-    name: Test
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v3
-      - name: Install dependencies
-        run: |
-          python3 -m pip install --upgrade -r python/wpt/requirements-dev.txt
-      - name: Running tests
-        run: |
-          python3 python/wpt/test.py