Mock methods with static return types

[ghostwriter]

This patch resolves #1155, via the following changes:

• Add tests and fixtures
• Mock methods with static return type.

class Foo
{
    public function getFoo(): static
    {
        return $this;
    }
}

[davedevelopment]

Thank you!

[ramsey]

Thanks, @ghostwriter!

[ruudk]

Thanks for this. Would be great to have this tagged 🙏

Edit: Created an issue to track this differently: #1161