Add custom ExecutionTimeTestListener

Enables to report long running test. The `phpunit.xml` supports the following settings:

- First argument enables/disables the output of the listener
- Second argument specifies the threshold in seconds as to when the listener should report a test.
```
<listeners>
<listener ...>
   <arguments>
      <boolean>true</boolean>
      <integer>10</integer>
   </arguments>
</listener>
</listeners>
```