perf ui browser annotate-data: Provide feedback on unhandled hotkeys

Don't just eat unknown keys without providing visual feedback and
instructions on how to see which ones are assigned.

Suggested-by: Ingo Molnar <[e-mail]>
Tested-by: Ingo Molnar <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: James Clark <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/ui/browsers/annotate-data.c

···
 		case CTRL('c'):
 			goto out;
 		default:
+			ui_browser__warn_unhandled_hotkey(&browser->b, key, delay_secs, ", use 'h'/F1 to see actions");
 			continue;
 		}
 	}