Remove special logic for user 1 in SwitchAccessCheck

I'll provide a patch for this in a moment.

The permission system should catch everything already.

As tests show it's right and one more clean-up for related 📌 Add a container parameter that can remove the special behavior of UID#1 Fixed

Have been building on the test coverage from 🐛 Masquerade as blocked user returns a 403 error and logs out the user RTBC and from what I can see the "Unmasquerade" link is always shown for user 1, even though $this->masquerade->isMasquerading() reports FALSE in UnmasqueradeAccessCheck::access(). Any thoughts on how we could resolve that? The attached patch sits on top of #3258364-31.

I wonder if the link showing up is because of caching, or because of something else, maybe something related to permissions?

And do we want to wrap that problem into this issue or spin it off as a separate issue?

Answering my own question: let's focus this issue on SwitchAccessCheck, and we'll do a separate issue on the unmasquerade link.

We can do the unmasquerade link problems in #3271001.

Made an MR from #3. Hiding patches.

MR is green, let's get 'er in!