[PP-1] Remove drupalorg_mockapi or move it to "test" folder

Problem/Motivation

The new live endpoint is now fully integrated. We should now do something with the old "drupalorg_mockapi". Either fully remove all the code around it (tests included?) or move the plugin to a test folder. If we go with the latter, what do we do with the fixtures going forward?

Proposed resolution

Clean up all the code regarding "drupalorg_mockapi" plugin.