make secret api more versatile

[TychoVrahe]

This PR refactors secret API to accommodate needs for more complex keys handling.

Secret API is unified to be independent on optiga/tropic presence, and a specific secret_keys extension is introduced to handle these specific keys.

Secret storage layout is now model dependent.

On U5, new key variant, public, is introduced: such keys are always provided to FW and are not erased on bootloader unlock.

On T3W1 we still use original secret layout with three keys stored, change to 'root key' and derivations are left to next work.

Ad review: @andrewkozlik and @onvej-sl as you will be working on the derivations, please look over the API to see if it can work. No need to go trough implementation details if you dont want to.

[github-actions[bot]]

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)
T3W1	test(screens) main(screens)	test(screens) main(screens)	test(screens) main(screens)
All	main(screens)

[TychoVrahe]

one more commit to: fix caching of potentially non-written public keys, and prioritize locked bootloader check in prepare_fw function: https://github.com/trezor/trezor-firmware/pull/5184/commits/6e8ed491d29b59a391dd7f90282aac08cff7b5b7

[cepetr]

one more commit to: fix caching of potentially non-written public keys, and prioritize locked bootloader check in prepare_fw function: 6e8ed49

LGTM

[onvej-sl]

I'm okay with the API.

[TychoVrahe]

Thanks, i will squash & merge after freeze unless more issues pop up