[SSH Node Pools] Make SSH Node Pools deploy run through current process

[kyuds]

With #8061 we have deprecated sky local up with ip lists, which shared a lot of the codebase with ssh node pools. Currently, these k3s clusters are deployed via a subprocess python script deploy_remote_cluster.py.

However, as we move to persist state in the db, etc, it is much more efficient to have ssh node pools be deployed within the skypilot process.

The decision to make it run in a subprocess python script was due to reusing various parts of the ip lists codebase, and now that this is no longer relevant, we don't have to make it into a subprocess. This also gives the added benefits of not needing to run log processors, etc.