fix(phpunit): PHPUnit 12 coverage source + valid schema for CI

Move includes to <source> (PHPUnit 12 no longer reads <coverage>/<include>).
Drop removed root attributes; use backupStaticProperties. Set
failOnPhpunitWarning=false so configuration warnings do not fail the build.

Co-authored-by: Zakhar <zahar.guzenko@gmail.com>

Author: cursoragent

phpunit.xml.dist

@@ -1,23 +1,22 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <phpunit bootstrap="vendor/autoload.php"
          backupGlobals="false"
-         backupStaticAttributes="false"
+         backupStaticProperties="false"
          colors="true"
-         verbose="true"
-         convertErrorsToExceptions="true"
-         convertNoticesToExceptions="true"
-         convertWarningsToExceptions="true"
          processIsolation="false"
-         stopOnFailure="false">
+         stopOnFailure="false"
+         failOnPhpunitWarning="false">
     <testsuites>
         <testsuite name="Behat Api Context Test Suite">
             <directory>tests</directory>
         </testsuite>
     </testsuites>
-    <coverage>
+    <source>
         <include>
             <directory>./src</directory>
         </include>
+    </source>
+    <coverage>
         <report>
             <clover outputFile="clover.xml"/>
         </report>