Coding Standards for PHP Stan Level 6 and PHP CS

There are a few points left:

• Missing cache backend declaration for performance.
• Drupal\drd\Drush\Generators\ActionPlugin extends the BaseGenerator class. There are undefined function calls.
• In, src/Entity/Account there are constants accessed in DRD Agent, which do not exist anymore.
• The new ECA Event implementation must be used.

The summary can be found here: https://git.drupalcode.org/project/drd/-/pipelines/42048/codequality_report

Fixed all issues except ECA 2.0 compatibility. That will follow next.

This is now completed and can be reviewed and merged.

This is strange, there is still an error in the pipeline which I can not reproduce locally:

------ --------------------------------------------- 
  Line   src/UpdateProcessor.php                      
 ------ --------------------------------------------- 
  483    No error to ignore is reported on line 483.  
 ------ --------------------------------------------- 
 [ERROR] Found 1 error  

Automatically closed - issue fixed for 2 weeks with no activity.