Inconsistent behavior with `class_string` of mocks for intersection types

Start with the makeInstanceReturnsClassInstance test and reproduce the reported diagnostic involving get_class(), getMock(), and GeneralUtility::makeInstance(). Trace how phpstan-phpunit represents the mock's class-string intersection versus the expected class-string; done means the valid test no longer produces this mismatch.

I have not been able to create a working example for this on the PHPStan playground as this bug involves PHPUnit and the phpstan-phpunit package.

We have a class with a generator function that looks like this:

    /**
     * Creates an instance of a class taking into account the class-extensions
     * API of TYPO3. USE THIS method instead of the PHP "new" keyword.
     * Eg. "$obj = new myclass;" should be "$obj = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance("myclass")" instead!
     *
     * You can also pass arguments for a constructor:
     * \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\myClass::class, $arg1, $arg2, ..., $argN)
     *
     * @template T of object
     * @param class-string<T> $className name of the class to instantiate, must not be empty and not start with a backslash
     * @param array<int, mixed> $constructorArguments Arguments for the constructor
     * @return T the created instance
     */
    public static function makeInstance($className, ...$constructorArguments)
    {…}

One of the tests for this method looks like this:

    /**
     * @test
     */
    public function makeInstanceReturnsClassInstance(): void
    {
        $className = get_class($this->getMockBuilder('foo')->getMock());
        self::assertInstanceOf($className, GeneralUtility::makeInstance($className));
    }

PHPStan (or phpstan-phpunit) now seems to mix up two different representations of a class string for a intersection types (which both look plausible to me, but they're not the same to PHPStan):

  3123   Parameter #1 $className of static method TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance() expects                                                       
         class-string<foo&PHPUnit\Framework\MockObject\MockObject>,
         class-string<foo>&class-string<PHPUnit\Framework\MockObject\MockObject> given.