Reading raw ADC data on ESP32 and ESP32-S2

[bjoernQ]

• implement ADC for ESP32 (basically a port of what ESP32-HAL had)
• implement ADC for ESP32-S2
  • only works in release mode - no idea why, most probably a codegen issue? Worth to analyze this later
• prepare ESP32-S3 for analog functions by adding the analog capable pins and .into_analog()

This doesn't implement ADC for ESP32-S3 since our SVD is still missing the SENS peripheral.

ESP32-C3 implementation will be done separately since it's very different and not to blow up this PR too much

[jessebraham]

Looks pretty good overall. I think there is probably some refactoring that can be done to reduce duplication a bit, but doesn't really make sense to do that until all implementations are there IMO.

I unfortunately am still unpacking some stuff and I can't find my soldering iron, so I'm unable to attach leads to the potentiometer I found :( I'm sure you tested it but just letting you know.