DAC

[zakary-bt]

Summary

DAC implementation for thumbv6m

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)

If Adding a new Board

• Board CI added to crates.json
• Board is properly following "Tier 2" conventions, unless otherwise decided to be "Tier 1"

If Adding a new cargo feature to the HAL

• Feature is added to the test matrix for applicable boards / PACs in crates.json

[jbeaurivage]

Note to anyone interested: I personally know the author of this PR, and it's highly unlikely that they come back to revisit it or even check on its status. Anyone is welcome to take ownership of it to try and get it completed!