Make sure test methods have `@test` annotation

[OndraM]

If we use @test annotations to declare test methods, you may forgot to add the annotation, leading to the test method being silently ignored and not executed.

    public function shouldDoSomething(): void
    {
         // ...
    }

We could make fixer to make sure public method starting with "should" (which is our convention for test method names) have the @test annotation. (This must apply only to PHPUnit test files, ie. files having "Test.php" suffix).

Also make sure we cover case when @test annotation is wrongly declared (missing space - /**@test */) and thus undetected by PHPUnit as test method.

Note - there is PhpCsFixer\Fixer\PhpUnit\PhpUnitTestAnnotationFixer, but it does only unifies the style, even with style set to "annotations", it won't detect methods missing the annotation.