Deprecate MediaProviderInterface::validate()

[dmaicher]

Subject

I am targeting this branch, because {reason}.

Relates to sonata-project/form-extensions#333

Changelog

### Deprecated
- `MediaProviderInterface::validate()` is deprecated. Implement `validateMedia()` instead. 

To do

• Add more tests
• documentation update?

@sonata-project/contributors this is a draft for now. Before I continue to finalize it I wanted to get your feedback on it.

To achieve sonata-project/form-extensions#333 we need to get rid of ErrorElement and InlineConstraint usages here.

From what I see we can easily achieve the validation with the proposed approach here by introducing a new validateMedia() method.

WDYT?

[VincentLanglet]

Seems an interesting solution, the only issue I see

• If it's really Backward compatible for someone overriding validate method (and eventually rely on parent::validate)

• We have BlockBundle using it a lot https://github.com/search?q=repo%3Asonata-project%2FSonataBlockBundle%20ErrorElement&type=code and every bundle implementing those interface. Like SonataPageBundle or SonataClassificationBundle.

• More important, with our lack of maintainer/contributor, I dunno if there will be a new major one day and when...

[VincentLanglet]

There is no BC break issue if someone is extending the validate method ?

[dmaicher]

It should be compatible as I added those checks if a child class overwrites them inside BaseProvider 🤔

[dmaicher]

* If it's really Backward compatible for someone overriding validate method (and eventually rely on parent::validate)

Should be. See #2499 (comment)

* We have BlockBundle using it a lot https://github.com/search?q=repo%3Asonata-project%2FSonataBlockBundle%20ErrorElement&type=code and every bundle implementing those interface. Like SonataPageBundle or SonataClassificationBundle.

Yeah that would indeed be the bigger work to deprecate and fix those 😢

* More important, with our lack of maintainer/contributor, I dunno if there will be a new major one day and when...

Valid point. Maybe its not worth it for now anyway. I don't use this bundle myself anyway.