Document instructions for configuring Ambient w/ gitops (i.e. waypoint proxies)

[MorrisLaw]

Context: In Istio 1.22 we have added a lot of new functionality that allows a user more control over how they configure their waypoint proxies. These changes can be confusing to users trying to leverage this new functionality manually or automated with something like gitops.

Issue: One specific example is enrolling waypoint in a namespace via istioctl experimental waypoint apply --enroll-namespace.

The issue is that some users may have confusion around how to confidently do this, especially when working with gitops. Typically, we'd rely on a user being able to istioctl experimental waypoint generate... to generate the yaml for the user to inspect before they decide to actually apply it. But for cases like --enroll-namespace it's not trivial to add generate support for that flag because the yaml can't be provided since in this case, we just want to patch it.

Task: An alternative solution to adding another generate command (if it's even possible) is to document how they can configure the waypoint proxy and provide some general instructions on how to use ambient w/ gitops.

[MorrisLaw]

cc/ @ably77

[craigbox]

If anyone has a chance to write this, I'll happily edit it and shepherd it into 1.23's docs.