Remote-SSH: Avoid connection reconnects on workspace change

If I am using remote-ssh on a workspace, and I switch to a different workspace on the same machine (eg: change from `~/workspace1` to `~/workspace2`), is there a way to avoid the "Setting up SSH host..."?

If the remote device already has the ssh connection set up, why does it need to close the connection and start a new one? reusing the connection would dramatically speed up this process when switching across multiple workspaces multiple times.

This is especially frustrating when dealing with multiple projects in the same monorepo. switching to a different project means I have to wait around 20seconds every time I switch

Start by tracing how Remote-SSH handles workspace changes and the “Setting up SSH host...” flow when switching between workspaces on the same machine. The change is complete when an existing SSH connection can be reused across workspace switches without restarting setup or introducing connection failures.

Written by the indexing model from the issue text.