[KIT-73] fn.pdb(args, kwargs)

[dongreenberg]

At one point we had breakpoints and pdb working using RPyC (it's still in function.py at 379). It might be worth trying to get that working again.

Another option barring that:

When user calls fn.pdb, start a new rpc server on the cluster on a different port and a new screen name (e.g. fn_name_timestamp), dedicated to this function. Then, start an ssh terminal into the cluster with `screen -r screen_name`.

Also could be worth exploring the pty approach Modal took.

Cc @Caroline

_{From SyncLinear.com | KIT-73}