Debugger: Implement remainder of #12729.

UserInterfaceListener:
- Add request hook for writing a core file. Implement in TeamDebugger.

Jobs/WriteCoreFileJob:
- Add new job to actually dispatch the core file request via the debugger
  interface.

Team{::Listener}
- Add listener event + hook for notifications when a core file gets written.
  Implement in CLI.

CliContext:
- Add event flag for core file changed.

CommandLineUserInterface:
- Add 'write-core' command. This optionally takes a path to write the core to,
  otherwise one is automatically generated by, similarly to debug reports. As
  such, one can now generate cores for things like app_server and registrar
  crashes if desired, in addition to reports.

src/apps/debugger/controllers/TeamDebugger.h

@@ -131,6 +131,8 @@ private:
 
 	virtual void				DebugReportRequested(entry_ref* targetPath);
 
+	virtual	void				WriteCoreFileRequested(entry_ref* targetPath);
+
 	virtual	void				TeamRestartRequested();
 
 	virtual	bool				UserInterfaceQuitRequested(
@@ -220,6 +222,8 @@ private:
 									StackFrame* frame,
 									::Thread* thread);
 
+			void				_HandleWriteCoreFile(const entry_ref& ref);
+
 			status_t			_HandleSetArguments(int argc,
 									const char* const* argv);