Master instance should not be registered as regular instance

[doerfli]

use own nft type instead of instance. so it does not mix with regular instances and can be easily distinguished.

[marcoatpaladin]

It looks like right now the InstanceService hardcodes these instances and does not use the registry. To my knowledge no other component uses the registry for the master instances.

The master instances could thus be dropped from the registry alltogether, or at least be kept in their own namespace within the registry, as they represent a different concept to the real instances.

[rapidddenis]

Also initialization of master instance can be made minimal (e.g. without access control configuration)