[API Change] Add Scope to the FederatedResourceQuota

[mszacillo]

What would you like to be added:

FederatedResourceQuotaSpec should support setting Scope, similar to the way ResourceQuota allows setting Scopes based on PriorityClass.

Why is this needed:

This is a follow-up item stemming out of #6486. The FederatedResourceQuota was enhanced to support quota enforcement on a federated level. However, the FederatedResourceQuota is currently tied to a single namespace.

It may be desirable to have multiple FederatedResourceQuotas in a single namespace, which would track quota usage for different scopes (defined by different PriorityClasses).

[RainbowMango]

Thank you! I added to the backlog.

PS:
Anyone who wants this feature, please leave a comment here, so that we can prioritize it.