[11.x] feat: add generics to tap() helper

[calebdw]

Hello!

This PR adds generics to the tap() helper so it properly knows the correct return type:

        // returned mixed, now returns RepositoryFake
        return tap(new RepositoryFake($feed), function ($fake) {
            static::swap($fake);
        });

I also went ahead and made some of the other tap methods more specific.

Thanks!

[calebdw]

Thanks @taylorotwell!