Fix false positive inheritance deprecation for embeddable subclasses

[isaackaara]

What

When an embeddable class extends another embeddable class, ClassMetadataFactory incorrectly triggers a deprecation warning about a missing inheritance mapping type declaration.

Why

The check at line 164 of ClassMetadataFactory::doLoadMetadata() only guards against isMappedSuperclass, but does not exclude embedded classes. Since embeddable classes cannot have inheritance mapping types, the deprecation should not fire for them.

Fix

Added && ! $class->isEmbeddedClass to the condition so the deprecation is only triggered for regular entity classes, not embeddables.

How to reproduce

/** @Embeddable */
class Timeframe {
    public function __construct(
        protected readonly ?\DateTimeImmutable $from,
        protected readonly ?\DateTimeImmutable $to,
    ) {}
}

/** @Embeddable */
class BoundedTimeframe extends Timeframe {
    public function __construct(\DateTimeImmutable $from, \DateTimeImmutable $to) {
        parent::__construct($from, $to);
    }
}

Before this fix, loading metadata for BoundedTimeframe triggers:

Entity class 'BoundedTimeframe' is a subclass of the root entity class 'Timeframe', but no inheritance mapping type was declared. This is a misconfiguration and will be an error in Doctrine ORM 3.0.

After this fix, no deprecation is triggered.

Fixes #11843

[github-actions]

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[greg0ire]

Sorry, 2.20.x is closed for bugfixes. Please retarget to 3.6.x