UNOQ: implement proper "wait for app" mode

[facchinm]

The current implementation of "Flash Mode=RAM" was meant to syncronize the startup of the microcontroller with an application launched by AppLab.
However, it has a bunch of limitiations which make it basically useless for bigger projects.

Replace it with another step of (gpio-based) syncronization, so AppLab can safely decide when to unlock the boot.

• Depends on the corresponding PR in arduino-app-cli
• Requires a rebuild+repackage of zephyr-sketch-tool

@lucarin91 @pillo79

[github-actions]

Built 0.53.2-0.dev+165f441

CI run PASSED 🟢

Artifact	Board	Core	Tests	RAM	Sketches	Warnings	Errors
✅* zephyr_contrib	ek_ra8d1	📗	✅*	11.9%	2	2	-
	frdm_mcxn947	3 🏷️	✅*	57.9%	2	2	-
	frdm_rw612	1 🏷️	✅*	83.0%	2	2	-
✔️* zephyr_main	giga	4 🏷️	✅*	54.5%	44	14	-
	nano33ble	1 🏷️	✅*	78.7%	22	10	-
	nano_matter	📗	✔️*	⚠️ 85.7%	20	10	(2*)
	niclasense	2 🏷️	✅*	⚠️ 87.1%	20	10	-
	opta	4 🏷️	✔️*	46.6%	54	26	(2*)
	portentac33	3 🏷️	✔️*	⚠️ 95.1%	56	28	(8*)
	portentah7	3 🏷️	✔️*	47.3%	58	28	(2*)
✅* zephyr_unoq	unoq	📗	✅*	26.3%	52	10	-

Legend

Board	Test	Status description
🔥	🔥	Test run failed to complete.
❌	🔴	Test completed with unexpected errors.
✔️*	🚫	Test completed with errors, but all are known/expected.
✅*	🟡	Test completed with some warnings; no errors detected.
✅	🟢	Test passed successfully, with no warnings or errors.
🌑	🌑	Test was skipped.

[lucarin91]

Maybe we should make this more robust by setting a max length of the LOW state, e.g., 200ms?

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