Improve remote debugging setup

[qubitron]

Including but not limited to:

• automatic copying of files
• Add default path mappings for remote debugging (Automatically infer local and remote path mappings for remote debugging #1385)
• setup over SSH (Automate SSH connections through launch.json configuration for Remote Attach #2641)
• automatic symbol detection (Automatically infer local and remote path mappings for remote debugging #1385)
• docker
• Validate remote IP and port (for attach)
• Debug existing remote python process? (Attach the debugger to a remote instance of python process #1669)
• what else?

[DonJayamanne]

@qubitron
Can we break this into separate sub-tasks & work on individual manageable & deliverable features. Else this is a large item.

Step 1: Attach

I believe the most basic feature we should work on is improving the existing attach scenario, and move on from there.

• When user hits debug button, we validate the remote IP and port are reachable
  • Prompt for IP and Port
• When user hits debug button, we always display the configuration UI

Pros:

• UI for use to enter info
• Information will be validated

Options for UI

1. Go ahead with standard (individual) VS Code style prompts.

• First prompt for IP, then port, then individual path mappings, etc...
• Cons: One prompt after another

2 Go ahead with a richer UI (similar to Jupyter)

• This isn't a hack, this is using VSC infrastructure to display custom UI.
  I believe this would be better as the UI would be richer.
• We'll need this for other complex debug configurations, such as configuring docker, or deploy and run (defining the paths, mappings, what local files need to be copied, etc).
  I.e. lots of configuration items, that would be best captured in a custom UI.
• Pro: Rich UX.

[luabud]

Closing as we now have the Remote - SSH extension.