Global management of graymail

Currently there is no way to manage graymail at the MSP/partner level. At the root team, we can create allow list entries for domains globally, but there is no equivalent for graymail.

This causes major banner fatigue across all customer teams. 8/10 graymail-tagged emails aren't meaningfully different from spam, confusing end users. Until there is a way to manage this globally, many MSPs are forced to disable graymail entirely.

Also requested: The ability to disable/enable graymail from the partner center, so MSPs don't have to manually toggle it per tenant when onboarding new customers.