[Catalog] Move GC functionality into Nessie Catalog

[snazy]

Having to configure all the Iceberg and potentially Hadoop configuration options for Nessie GC is not particularly convenient. Nessie Catalog has all the object storage configurations and has access to the credentials.

Nessie GC is not extremely memory hungry, it is rather "just" a time consuming process that requires a lot of object storage I/O.

Moving Nessie GC into Nessie Catalog feels like a natural follow-up, which eliminates a lot of configuration headaches.

It needs to be explored whether change is a feasible option in multi-tenant scenarios.