Zephyr 4.1

[jalinei]

Zephyr 4.1 is out and available for platformIO.
https://github.com/platformio/platform-ststm32/releases/tag/v19.1.0

We should try compiling with it and see if any breaking changes.

v4.1 is interesting because zephyr team fixed major performance issues.
Would be great to benchmark that.