Perform remote validation before launching the debugger

[softworkz]

Problem

In the issue #67, I have described some of the problems I've run into when trying to use the extension.

The log output is often not really helpful to understand which problems exist.

Proposed Solution

Execute a script via SSH (the exact connection that the debugger will use) which is checking for a number of potential problems and - in case - provide a clear message (in a MessageBox) about the detected problem(s)..

The following checks come to my mind:

• SSH connection is working
  otherwise show the command output, possibly after kill (when it waits for user input)
• dotnet can be executed
  either with or without path
• A matching dotnet runtime or SDK is installed
  dotnet --info shows that
• The VS remote debugger is installed at the configured path
• The target app is deployed to the configured path
• Up-to-date check: The local compile output (primary exe/dll) is not newer than the remote copy

[MichaelKoster70]

The inner loop (deploy / debug) should be as quick as possible. So I will not add these checks to the normal debugger launch process

Instead, I will add a new command "Verify/Diagnose) that does all the above checks