Debugger: Cleanups.

General:
- Move all smaller prompt/edit windows to a dedicated subfolder.

Debugger/TeamsWindow/StartTeamWindow:
- Move management of StartTeamWindow to application, rather than
  Teams window.

TeamWindow:
- Add top level menu item for commands that aren't specific to the
  current team. This currently consists of requesting that the
  Teams window be shown, and directly starting a new team.

Fixes part of #11659 (no way to start additional teams if Debugger was
initially started with a specific team).
debug_server: Fix #11659.

- If we're asked to debug a team graphically, check if Debugger is already
  running. If so, send it a message asking it to debug the team rather than
  trying to invoke it by command line, as the latter will simply result in
  a B_SILENT_RELAUNCH message, and won't actually process the request properly.