Remove reporting of deprecated method calls in tests flagged as @group legacy

[stof]

symfony/phpunit-bridge defines a convention where adding @group legacy on a test (either by adding it on the method or on the class as PHPUnit considers that a @group added on a class applies to all tests defined in that class) disables the reporting of deprecations in that test, as this test is about covering the legacy behavior (and so using deprecated APIs is expected).

phpstan/phpstan-deprecation-rules#99 has added an extension point allowing to implement such feature. It would be great to provide an implementation of the interface following this convention.

[stof]

This was initially requested in phpstan/phpstan-deprecation-rules#64, which end up introducing the needed extension point. But solving this entirely actually require using the extension point, not just introducing it.

[staabm]

the implementation is described in the docs phpstan/phpstan-deprecation-rules@7d78404...27397cd#diff-b335630551682c19a781afebcf4d07bf978fb1f8ac04c6bf87428ed5106870f5R56-R81

so your request is to ship this documented default impl with the phpstan-symfony extension?

[stof]

Yes. As this is a Symfony convention, it might make sense to ship it in phpstan-symfony automatically.

[stof]

Note that the shipped implementation should be a little more involved IMO:

• it should check the class docblock as well (as groups might be defined at the class level too)
• it should probably apply only in classes extending PHPUnit\Framework\TestCase as this @group legacy has an effect only in tests.