Add Schema limits

[tillrohrmann]

Currently, the Schema object can grow unboundedly because we don't enforce limits. If the Schema grows too big, then our grpc based metadata communication fails as it by default has a message size limit of 4MB. This can happen if users have many historic deployments registered, for example.

A user reported this problem: https://discord.com/channels/1128210118216007792/1446088397398610022

To protect against this problem, we should add some limits:

• Limit the overall size of the Schema object. It should be below the maximum message size that our grpc clients are configured with.

Once we hit the limit, we should print a comprehensive error message telling the user to remove unused deployments to reduce the overall size.

[slinkydeveloper]

I do understand why we need this, and definitely what we have now is bad as the user remains "locked up" from the schema registry.

Neverthless, If it's possible, I would instead consider finding a solution to the 4MB limitation.

Once we hit the limit, we should print a comprehensive error message telling the user to remove unused deployments to reduce the overall size.

This is generally not a bad idea, but I think the problem with this is that we don't have yet a good story around deployment removal.
Users needs to do the -f, and UI will require double confirmation, without even checking if you got pending invocations to it.
Plus this is gonna get a awful worse when auto registering:

• When using the k8s operator. In this case i'm not even sure what will happen?!
• When using github actions. In this case, at least it's gonna be "easier" to notice for the user I assume, they see the red cross on the github repo 🤷.

I had a task here tracking the "deployment removal" problem and how to iterate over it: #3935