Add support for adding the #[Override] attribute to methods implementing interfaces

[hockdudu]

This pull request adds an opt-in configuration flag to AddOverrideAttributeToOverriddenMethodsRector to also add #[\Override] on methods implementing interface methods.

The default behavior is unchanged. The existing special handling of Stringable in combination with allow_override_empty_method is preserved.

It also fixes an edge case where the presence of Stringable caused #[\Override] to be added to unrelated interface methods (example 1, example 2). Tests were added to prevent regressions.

Motivation:

• PHP accepts #[\Override] for both parent methods and implemented interface methods
• Some tooling expects or suggests the same behavior

This allows projects to opt in without affecting existing users.

New config:

use Rector\Config\RectorConfig;
use Rector\Php83\Rector\ClassMethod\AddOverrideAttributeToOverriddenMethodsRector;

return RectorConfig::configure()
    ->withConfiguredRule(AddOverrideAttributeToOverriddenMethodsRector::class, [
        AddOverrideAttributeToOverriddenMethodsRector::ADD_TO_INTERFACE_METHODS => true,
    ]);

Fixes rectorphp/rector#9699

[TomasVotruba]

Thanks for the optional parameter 👍 Seeing so much support for this feature, let's give this a go :)