Refactor branch: updates needed to support os.fork

[karthiknadig]

1. settrace_forked should use settings similar to settrace in _enable_attach

wait_for_ready_to_run=False,
block_until_connected=False,

2. forked processes should notify parent about the port to communicate on.
3. forked processes should wait for a response from parent on should they continue or not.

[karthiknadig]

We will also need to update _on_forked_process so that the forked process can connect to parent process, since it wont receive the host and port via CLI.

[karthiknadig]

We decided we want to take a common approach for os.spawn and os.fork sub-processes. we will update here when we have settled on a design.

[karthiknadig]

Closing this in favor of the epic we have to handle multiprocessing: #1706