Convert EntityReferenceSelection plugin discovery to attributes

This will fail with phpstan errors. One is about the deliberately broken plugin and another is for the missing '$deriver' property.

fixed phpstan issues

Appears to have several test failures.

fixed

Appears all instances and feedback has been addressed.

Added some comments to the MR>

Suggestions appear to added

I had to make some changes to the MR in order to benefit from attributes. Weight and group are now required. Annotations was quite loose so we couldn't enforce this properly there but now we can. I don't think that the broken handler should cause to make them optional - given how the broken handler works - see \Drupal\Core\Entity\EntityReferenceSelection\SelectionPluginManager. We can provide some defaults in that plugin that are going to be ignored.

Update using weight and group didn't break anything.

Committed to 11.x and backported to 10.3.x

larowlan → closed merge request !6638

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