add max_content_depth limit

[lferran]

This PR does:

• Adds a configurable limit (max_content_depth) on height of the objects tree.

The motivation behind it is because there are some recursive functions in guillotina ( see cached_principal_perimssion, for instance) where if we don't put a limit, we could run into python throwing RecursionError. We've found this at Onna.

I'll forward-port once we agree on the solution and it's merged.

[vangheem]

@bloodbare @masipcat how do you feel about this?

[masipcat]

It's ok for me to add it, but I think it's still possible to bypass this restriction when moving folder