dap: support suspendDebuggee in multi-client mode

[polinasok]

Upstream dependency at https://github.com/microsoft/vscode/issues/134412 is in, so we can now provide this in our DA to give people more disconnect options.

- disconnect            = leaves debugger and target running (default)
- disconnect + suspend  = leaves debugger and target suspended
- stop                  = kills  debugger and target

Updates #2772

[polinasok]

Actually give me a moment to revise something before reviewing.

[derekparker]

Going to close for now due to inactivity. Please reopen if this is still necessary / planned to be worked on.