ingress: Correct FromGroups rule Parsing

[Alex-Waring]

In https://github.com/cilium/cilium/pull/30708 I created a resource that translates to a K8s resource but not to an actual resource. This PR corrects that behaviour by adding in some tests and fixing when they break. You could argue I should have done this initially, you're right.

This should be backported to 1.16 so it goes out with the original PR.

[joestringer]

/test

[Alex-Waring]

@learnitall / @joamaki I don't think the test failures are related, mind a review please?

[joestringer]

This should be backported to 1.16 so it goes out with the original PR.

For now, v1.16 development continues on the main branch so no special process is required to ensure the above.

[squeed]

Unfortunately, this will need a rebase. But thanks for catching this!

Since this is fixing an unshipped bug, no release note is required.

[aanm]

/test