add brightness setting

[TychoVrahe]

building on #3483, but adding support for mercury

[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)
T2B1 Safe 3	3280	test(screens) main(screens)	2724
T3T1	test(screens) main(screens)	test(screens) main(screens)	test(screens) main(screens)
All	main(screens)

[github-actions]

legacy UI changes	device test(screens) main(screens)

[matejcik]

two high level comments (also mentioned in the review):

(a) perhaps there should be a SetBrightness call as opposed to shoving it into settings? depends on whether we ever want the user to set brightness from host
(if we do, the handling for that is completely missing)

(b) I would avoid exposing to Python. I can take over that part if you like

[matejcik]

@TychoVrahe please check my changes
you can ignore 86bc1ad, it is a cherry-pick from main, i needed it for vscode

[obrusvit]

Don't we miss also T3T1 specifics?

[matejcik]

ah, this is a cherrypick of cf58fdd from main. we probably should, but this commit should be removed from the PR before merging, and someone should add T3T1 features when merging the UI branch into main (or later, whenever we hit a problem caused by it, so probably when you try to run T3T1 Rust tests)

[obrusvit]

Note: copy of model_t version. Should be reworked for mercury when design done.
Linking it here for now: #3748