Update PHPUnit testsuite names to use package names

Changes testsuite names from "default" to the respective package names:
- symfony/ai-agent
- symfony/ai-bundle
- symfony/mcp-bundle
- symfony/mcp-sdk
- symfony/ai-platform
- symfony/ai-store

Author: OskarStark

phpunit.xml.dist

@@ -11,7 +11,7 @@
          failOnRisky="true"
          failOnWarning="true">
     <testsuites>
-        <testsuite name="default">
+        <testsuite name="symfony/ai-platform">
             <directory>tests</directory>
         </testsuite>
     </testsuites>