Releases for A/B Test UI

First stable release. Contains: Cleanup, fixes, Drupal 9 compatibility and frontend tooling upgrade.

Fixes:

• #3068973: Database error when trying to save a URL greater than 64 characters
• Fix "Warning: count(): Parameter must be an array or an object that implements Countable" on the test list page.

Misc: PHPStorm cleanups for php, js, composer.

Most of the GA module related code has been moved to a submodule (it will be re-enabled via a hook update).

This shed light on some serious issues with the extensibility of the module, so some refactoring is going to happen.
There were minor CS fixes and some minor optimizations, too.

Replace \Drupal::time() with REQUEST_TIME for 8.2 core compatibility.

First non-dev release.
No new features are planned before making it stable, only small text updates, cleanup, etc.