Friendlier way to confirm long messages

[ibz]

This applies to all: btc sign-message, btc verify-message, ethereum sign-message, ethereum verify-message models T, TS3 and TS5.

The general idea is: if the message to be signed/verified can fit on 5 pages, we let the user scroll through the whole message. If the message is longer than 5 pages, we let the user confirm the message immediately or scroll through all pages.

Note: the difference between sign-message and verify-message is that sign-message uses "hold to confirm". This turned out very complex to achieve on model T in the case of long messages, so we decided to introduce an extra warning screen in that case, to replace the "hold to confirm" (model T, signing long message).

[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)