add second undocumented IOSET: UndocIoSet2

[Josfemova]

Summary

• It was necessary to add a new undocumented IOSET to the hal, as the ItsyBitsy m4 uses PA00, PA01 (IOSET 4), PB22 & PB23(IOSET 3) for Sercom1. This configuration is not listed as a valid combination in the datasheet, but works regardless. Similar to Port pygamer to v2 #455. Closes Can't configure Itsybitsy m4 default SPI with sercom::v2 (new undoc ioset perhaps?) #545.

Checklist

• CHANGELOG.md for the BSP or HAL updated
• All new or modified code is well documented, especially public items
• No new warnings or clippy suggestions have been introduced (see CI or check locally)