For the HAL, currently just passes the feature to the PAC. Also pass the 'rt' feature through to the HAL for all the BSP crates.
Bring in line with atsamd-hal GPIO v2 Copied as much as possible. Docs lifted mostly as-is. Also add sample BSP for the Feather RP2040 in boards/feather_rp2040 May include a few random fixes from currently futile attempt to get doctests working.