Debugger: Fix team restart request.

UserInterface:
- Add Clone() function to set of required virtuals. This asks the subclass
to create a new instance of its respective type.

{CommandLine,Graphical,Report}UserInterface:
- Implement the above function.

TeamDebugger:
- Add accessor for the currently active UI.

TargetHostInterface:
- Set correct request type when setting up the options for a team restart.
- Ask the TeamDebugger for its user interface and clone it in order to fill
in that aspect of the debug options. This fixes a regression introduced in
commit 880a64, which inadvertently resulted in team restarts no longer
working.

Debugger: Refactor non-interactive report handling.

- Add dedicated ReportDebugger application class for the case where we're
asked to do nothing more than save a report. Also add a corresponding
UserInterface subclass whose sole purpose is to take those necessary
actions and then exit.
- When the debugger is invoked via the --save-report option, we now start
via the aforementioned report/interface rather than piggybacking on the
CLI.
- Clean up CommandLineUserInterface/CliContext to remove handling for the
report saving option.

Should hopefully resolve #12155.

Debugger: Refactor non-interactive report handling.

- Add dedicated ReportDebugger application class for the case where we're
asked to do nothing more than save a report. Also add a corresponding
UserInterface subclass whose sole purpose is to take those necessary
actions and then exit.
- When the debugger is invoked via the --save-report option, we now start
via the aforementioned report/interface rather than piggybacking on the
CLI.
- Clean up CommandLineUserInterface/CliContext to remove handling for the
report saving option.

Should hopefully resolve #12155.