test: migrate to Yoast WP test utils and work around incompatibilities

.github/workflows/test.yml

@@ -13,9 +13,9 @@ jobs:
           - php: '8.1'
             wordpress: '6.1'
           - php: '8.0'
+            wordpress: '6.0'
+          - php: '7.4'
             wordpress: '5.9'
-          - php: '7.2'
-            wordpress: '5.0'
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -25,7 +25,7 @@ jobs:
           php-version: ${{ matrix.php }}
           tools: composer
       - name: Setup DB
-        run: sudo /etc/init.d/mysql start
+        run: sudo sudo systemctl start mysql.service
       - name: Setup WP
         run: bash bin/install-wp-tests.sh wordpress root root localhost "${{ matrix.wordpress }}"
       - name: Install