[CodeQuality] Skip mock property removal when used in a trait

[TomasVotruba]

RemoveNeverUsedMockPropertyRector removed a mock property when it saw no local uses. But a used trait can reference that property, so removal broke the code.

Now resolves each used trait's AST and skips removal if the trait fetches the property.

Skipped case

trait UsesMockPropertyTrait
{
    public function useMock(): void
    {
        $this->mockProperty->someMethod();
    }
}

final class SkipIfUsedInTrait extends TestCase
{
    use UsesMockPropertyTrait;

    private MockObject $mockProperty;

    protected function setUp(): void
    {
        $this->mockProperty = $this->createMock(\stdClass::class);
        $this->mockProperty->expects($this->once())
            ->method('someMethod')
            ->willReturn('someValue');
    }
}

Before this change the $mockProperty (and its setUp() assignment) got removed, breaking UsesMockPropertyTrait. Now it is kept.