Add ATtiny 817 support

[G33KatWork]

This patch adds support for the Attiny817.

This change depends on a patch that I just submitted to svd2rust: rust-embedded/svd2rust#784

I implemented a more convenient method to modify the configuration change protected registers that show up in these new cores. Unfortunately, you still need to define these registers manually for every single chip like I do in ccp.rs in this patch. There might be a way to get this information from the ATDF, carry it over into the SVD and then generate that as well using svd2rust. However, it's only a handful of registers for every chip, so I didn't look too much into it.

This might be applicable to other chips that are already supported in this crate like the ATtiny816 or 1614. Essentially all the new cores have some of these protected registers.

[G33KatWork]

It doesn't look like anybody upstream in svd2rust wants to merge this CCP stuff, so I am going to close this here and submit a PR for the Attiny417/817/1617/3217 in a few minutes without the CCP things.

I looked through the SVD spec to figure out if we can properly support generating code to write to CCP-protected registers, but I can't seem to find a viable solution.