Add Zephyr support and migrate to Arduino_Video

[leonardocavagnis]

This PR adds Zephyr support and migrates the backend from Arduino_H7_Video to the new Arduino_Video library (WIP & private). This change ensures dual compatibility for both Zephyr and mbed core.

Example status:

Example	Status	Notes
Backlight	✅	Fully functional.
Basic	✅	Requires Arduino_Video.
Camera	❌	Requires porting arducam_dvp library to Zephyr.
GFX	✅	Requires GigaDisplay_GFX PR #11.
IMU	❌	Porting exists, but initialization fails on available hardware (both mbed/Zephyr), needs investigation.
LVGL	✅	Requires Arduino_Video.
Microphone	❌	Requires porting the PDM library to Zephyr.
RGB	✅	Fully functional.

[CLAassistant]

All committers have signed the CLA.