Low power support for RP2350

[tannewt]

The SDK doesn't have an official API for it yet. So, we can wait or DIY it.

[tannewt]

Reference code is linked to (and discussed) in this issue: raspberrypi/pico-examples#530

[matemaciek]

Might be usefull: https://github.com/earlephilhower/arduino-pico/pull/2620/files

[dmcomm]

I'm trying to run an RP2040 program that uses sleep_memory to pass data between resets and between boot.py and main program, but doesn't actually use any of the low-power features. Not sure if this is a common situation or not.

[bablokb]

@eightycc: since you self-assigned this, please have a look at my PR. It works fine on all of my systems. And in contrast to the discussion, it does not "change semantics" (except for a single academic border case which is not relevant for any practical real-life scenario).

It does change the documentation bringing it in line with reality. The docs currently claims things that the code does not stand up to and never will ("It does not shut down WiFi, BLE, or other communications, or ongoing activities such as audio playback").