[3.x] Add deprecation notices related to validate methods

[tambait]

Subject

I am targeting this branch, because BC.

Closes #6233

Changelog

### Deprecated
- `AdminInterface::validate` method specification
- `AbstractAdmin:validate` method implementation
- `AbstractAdmin::attachInlineValidator()` method
- `AdminExtensionInterface::validate()` method specification
- `AbstractAdminExtension::validate()` method implementation

[VincentLanglet]

Can you add consign for the master branch ?

We generally add NEXT_MAJOR comment for this.

For instance

/**
     * Attach the inline validator to the model metadata, this must be done once per admin.
     *
     * NEXT_MAJOR: Remove this method.
     *
     * @deprecated since sonata-admin/admin-bundle 3.81
     */
    protected function attachInlineValidator()

Same can be done for validate, prevalidate, ... (all the methods you're deprecating).
And then, I think the PR will be ready.

[tambait]

Same can be done for validate, prevalidate, ... (all the methods you're deprecating). And then, I think the PR will be ready.

Thanks. I wanted to ask about prevalidate should it be depreciated also, I saw it only now. Its used in buildForm method in AbstractAdmin.

[VincentLanglet]

You should also deprecate AbstractAdmin::validate

And AbstractAdmin::preValidate I think (and remove it from LifecycleHookProviderInterface.)

[VincentLanglet]

The phpstan errors are normal ; I recommend to ignore them with a @phpstan-ignore-next-line

[VincentLanglet]

Thanks tambait

[franmomu]

@tambait thanks for your contribution!

Since in this PR we're introducing some deprecations, can you please update the issue description adding a changelog with these deprecations (like #6510 for example)?

I've created #6621 to fix some comments.

[tambait]

@franmomu

Since in this PR we're introducing some deprecations, can you please update the issue description adding a changelog with these deprecations (like #6510 for example)?

I've created #6621 to fix some comments.

Thanks. Does it make sense to list both method specification and implementation when they are in different classes like I did?

[franmomu]

Thanks, I think it does, for some reason we can remove a method from the specification but leave it in the implementation, I prefer being explicit.