Instances could do a better job of identifying if they're satisfying affinity requests or not

[smklein]

See: #7447 (comment)

Currently affinity/anti-affinity rules are used during the "sled reservation" component of VMM starting, but are not subsequently checked.

However, with permissive rules, it's possible that these affinity/anti-affinity requests are violated, and later could be re-inspected.

This issue tracks exposing an API to identify: "Is this instance satisfying affinity rules?"

Related, we could expose an API to identify: "Are there any instances violating affinity rules?"

[askfongjojo]

What will be very useful is to have the API at least return all the affinity/anti-affinity groups an instance is associated with (if determining whether the constraints are satisfied is too expensive to do). When an instance can't be started because the user has misconfigured the groups, it'll be very handy to get all groups with a single CLI command or see them on the Settings tab in the Instance UI.

[smklein]

What will be very useful is to have the API at least return all the affinity/anti-affinity groups an instance is associated with (if determining whether the constraints are satisfied is too expensive to do). When an instance can't be started because the user has misconfigured the groups, it'll be very handy to get all groups with a single CLI command or see them on the Settings tab in the Instance UI.

I went ahead and implemented this in #7857