Adds method to migrate operators from existing middlewares.

[steven2308]

This will be needed to register symbiotic operators the first time meta middleware is deployed.
It can be removed afterwards.

[NindoK]

I thought this was going to get called directly by the middleware? Why by the admin? It would make sense to do everything on chain from the middleware and make those onlyRole admin

[NindoK]

By doing this we don't even have to pass the address of th emiddleware, but we just check that the sender is a known middleware

[NindoK]

I'd rather do from each middleware rather than admin

[steven2308]

I'd rather do from each middleware rather than admin

I think you are missing the context of this task. This is to migrate.
When we deploy the middleware, Symbiotic will already have tens of operators. We will call this method once to migrate them so they are also tracked in the meta middleware, then we remove the method.

The rest of operations: register, unregister, update key, will call this directly. The methods for that already exist and must be called by the middlewares directly.