sql: move system.zones into the tenant keyspace

[arulajmani]

Is your feature request related to a problem? Please describe.

Part of #66348. We need to adsystem.zones for each tenant, and massage the existing zone config generation code to work off of descriptor IDs (instead of SystemTenantObjectIDs that it does today).

[ajwerner]

into the tenant keyspace and massage the existing zone config generation code to work on descriptor IDs (instead of system tenant object IDs as it does today).

I feel like this is a bit misleading. Is there really anything to be done? What is an object ID if not just a descriptor ID (plus some fake placeholder IDs)? What makes anything system tenant?

[arulajmani]

Is there really anything to be done? What is an object ID if not just a descriptor ID (plus some fake placeholder IDs)? What makes anything system tenant?

I was hoping to get rid of the concept of:

cockroach/pkg/config/system.go

Line 42 in 15ee387

type SystemTenantObjectID uint32

once system.zones moves into the tenant keyspace. It's merely a wrapper around descriptor IDs, so there isn't much here other than cleaning up all places that convert descriptor IDs to this type.

[irfansharif]

#67323.