feat(core/prodtest): Allow prodtest to exit from interactive mode

[kopecdav]

Add an option to exit from prodtest interactive mode with ".+ENTER" command.

If test script or test equipment connects to prodtest serial, it may happen that somebody already switched it to interactive mode before. To make it easier for it, it may switch back to non-interactive mode and don't deal with the colored responses etc.

Prodtest will confirm the exit command with OK in standard mode to be well machine readable.

[github-actions]

core UI changes	device test	click test	persistence test
T2T1 Model T	test(screens) main(screens)	test(screens) main(screens)	test(screens) main(screens)
T3B1 Safe 3	test(screens) main(screens)	test(screens) main(screens)	test(screens) main(screens)
T3T1 Safe 5	test(screens) main(screens)	test(screens) main(screens)	test(screens) main(screens)
All	main(screens)