[no-commit] Define a Rector rule to convert test annotations to attributes

Problem/Motivation

In PHPUnit 12, we have to replace test annotations with attributes. As noticed in #3417066-120: Upgrade PHPUnit to 10, drop Symfony PHPUnit-bridge dependency,

we can't mix PHPUnit attributes and annotations [in a single file], we will have to convert them all at once unfortunately

with thousands of test classes in Drupal, we should try to automate the conversion, in a way that a script can be executed on a file and convert it end-to-end.

Rector can help, but we need an overall Rector script that will do all the changes necessary in a go - we should convert by files or group of files, and not by rule/annotation.

Listing some findings for the Rector rule, will document here along

• @group legacy is a symfony/phpunit-bridge concept. It must be converted to the #[IgnoreDeprecations] attribute, however:
• it is still undocumented: https://github.com/sebastianbergmann/phpunit-documentation-english/issue...
• PHPStan does not identify this attribute as a deprecated scope https://github.com/phpstan/phpstan-deprecation-rules/issues/109
• @coversDefaultClass and @covers needs complete rethinking as there is NO one-to-one conversion:
• https://github.com/sebastianbergmann/phpunit/issues/4502
• https://github.com/rectorphp/rector-phpunit/issues/149
• https://github.com/sebastianbergmann/phpunit/issues/5175
• Rector rule CoversAnnotationWithValueToAttributeRector may not be fit for purpose because (a) does not manage short class names + use import and (b) it does not take into account the existence of [#CoversMethod] that was only (re)introduced in PHPUnit 11.1
• The #[CoversMethod] attribute only targets test classes and not individual test methods, this is being disputed upstream: https://github.com/sebastianbergmann/phpunit/issues/5837
• --> Since we will have to live with tests in shape for execution in PHPUnit 10 for a while, and only get later to a supported coverage of methods, the suggestion is to change @covers instances to @legacy-covers in the mean time, then decide what to do once fully on PHPUnit 11.
• @medium can no longer be associated to a method --> add #[Medium] to the class instead
• @uses can no longer be associated to a method --> add #[UsesClass()] to the class instead
• more to be defined

Proposed resolution

The MR here contains the rector.php file with a custome rule to do the conversion, and a .gitlab-ci.yml CI configuration file with a script that executes the rector rule, then runs PBPCBF to cleanup the changed files, then produces a git diff patch file and finally stores the patch as an artifact.

The diff patch file can then be used in child issues to convert specific parts of the test codebase.

The MR itself is not meant to be committed.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet