Fix PHPStan L1 errors "Annotation "@covers::foo" is invalid, "@covers" should be followed by a space and a value."

Problem/Motivation

Amongst the current suppressions found in the PHPStan level 1 baseline, introduce by the adding of phpstan/phpstan-phpunit, is: Annotation "@covers::foo" is invalid, "@covers" should be followed by a space and a value..

This issue exists to fix all of those.

Steps to reproduce

- Run PHPStan on level 1 and see the above issue amongst all others.

Proposed resolution

- Solve all of the reported issues for the above mentioned.
- Run PHPStan on level 1 and don't see the above issue any more.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet