Implement support for restarting teams.

- TeamDebugger's listener interface now exports a
TeamDebuggerRestartRequested hook. The latter is used to request
starting a new debugger instance with the same arguments/settings as the
team it represented. Implemented for the graphical debugger.

- When a team terminates, the resulting dialog now allows the user to
choose to quit, restart, or simply do nothing. The latter option still
needs some work though, as e.g. setting additional breakpoints currently
fails since the corresponding debugger interface is no longer around.

Implements the main part of #9774.