[CI] Explore fixing two notoriously flaky tests

[adamziel]

Motivation for the change, related issues

Cleans up resources in two, notoriously flaky unit tests to make them more reliable:

• Cleans up resources, calls php.exit()
• Stops the server to free up the port
• Updates the Xdebug DBGP integration test to use an ephemeral port
• Adds a handshake timeout and improved error handling for the DBGP server
• Ensures the tests fails gracefully when the handshake is not completed in time.

The tests we're trying to fix:

  ⎯⎯⎯⎯⎯⎯⎯ Failed Tests 2 ⎯⎯⎯⎯⎯⎯⎯
  
   FAIL  src/test/php-dynamic-loading.spec.ts > PHP 8.0 > XDebug > communicates with default DBGP port
   FAIL  src/test/php-networking.spec.ts > PHP 8.0 > cURL > should support multi handle requests
  Error: Test timed out in 20000ms.

Testing Instructions (or ideally a Blueprint)

CI :)