Merge branch 'hotfix/#6902-plugin-manager-auto-invokables-should-reject-non-existing-classes'

Close #6902
PHPCS
Added a failing test for #6893
Resolved the issue with the Zend\Code\Scanner\ClassScanner not properly identifying the ";" as the end of a abstract method.
Added the missing test asset.
Merge branch 'hotfix/#6901-class-scanner-broken-with-abstract-methods' into develop

Close #6901
Close #6893
Forward port #6901
Forward port #6893