Improve power saving (Requesting Pow-U users to test this)

[gskjold]

In an attempt to resolve edge cases where Pow-U reboots due to brown out, I've restricted certain operations based on Vcc. The changes look promising in my test environment, but I'd like more people to try this firmware to ensure that I have not accidentally broken something. Please let me know how this works for you guys in a weeks time:

esp32.zip
esp32c3.zip
esp32s2.zip
esp32s3.zip
esp32solo.zip
esp8266.zip