Issue #3507536: Switch to conditional usage of PHPStan for upstream incompatibilities

Closes #3507536

phpstan/baseline-no-getExtras.neon

+parameters:
+  ignoreErrors:
+    -
+       message: "#^Call to function method_exists\\(\\) with 'Drupal\\\\\\\\Core\\\\\\\\Recipe\\\\\\\\Recipe' and 'getExtra' will always evaluate to (true|false)\\.$#"
+       paths:
+         - ../src/Activator/RecipeActivator.php
+         - ../tests/src/Kernel/RecipeActivatorTest.php
+    -
+       message: "#^Call to an undefined method Drupal\\\\Core\\\\Recipe\\\\Recipe\\:\\:getExtra\\(\\)\\.$#"
+       paths:
+         - ../src/Activator/RecipeActivator.php