Debugger: Cleanup.

- Split MessageCodes.h into a second file that separates out the
application-specific message codes from those used by the core.
Adjust includes accordingly. No functional change.

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).

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).