GH Actions: update PHP ini configuration

Add `display_startup_errors=On` as per the current recommendation from PHPUnit.

Ref: sebastianbergmann/phpunit-documentation-english@b3b159c

Author: jrfnl

.github/workflows/test.yml

@@ -103,9 +103,9 @@ jobs:
           # On stable PHPCS versions, allow for PHP deprecation notices.
           # Unit tests don't need to fail on those for stable releases where those issues won't get fixed anymore.
           if [ "${{ matrix.phpcs_version }}" != "4.x-dev" ]; then
-            echo 'PHP_INI=error_reporting=E_ALL & ~E_DEPRECATED, display_errors=On, zend.assertions=1' >> $GITHUB_OUTPUT
+            echo 'PHP_INI=error_reporting=E_ALL & ~E_DEPRECATED, display_errors=On, display_startup_errors=On, zend.assertions=1' >> $GITHUB_OUTPUT
           else
-            echo 'PHP_INI=error_reporting=-1, display_errors=On, zend.assertions=1' >> $GITHUB_OUTPUT
+            echo 'PHP_INI=error_reporting=-1, display_errors=On, display_startup_errors=On, zend.assertions=1' >> $GITHUB_OUTPUT
           fi
 
       - name: Install PHP
@@ -188,9 +188,9 @@ jobs:
           # On stable PHPCS versions, allow for PHP deprecation notices.
           # Unit tests don't need to fail on those for stable releases where those issues won't get fixed anymore.
           if [ "${{ matrix.phpcs_version }}" != "4.x-dev" ]; then
-            echo 'PHP_INI=error_reporting=E_ALL & ~E_DEPRECATED, display_errors=On, zend.assertions=1' >> $GITHUB_OUTPUT
+            echo 'PHP_INI=error_reporting=E_ALL & ~E_DEPRECATED, display_errors=On, display_startup_errors=On, zend.assertions=1' >> $GITHUB_OUTPUT
           else
-            echo 'PHP_INI=error_reporting=-1, display_errors=On, zend.assertions=1' >> $GITHUB_OUTPUT
+            echo 'PHP_INI=error_reporting=-1, display_errors=On, display_startup_errors=On, zend.assertions=1' >> $GITHUB_OUTPUT
           fi
 
       - name: Install PHP