Decide where efuses code should live

[SergioGasquez]

          > I'm also aware that we also have some efuse field generation in esp-hal's xtask, is the plan to retire that and keep field generation here and periodically copy the (presumably the .rs) files over to esp-hal?

I don't know what the plan is, meant to bring this up in the original comment. Probably it's not a bad idea to even have a separate esp-efuse package or something, but as we were discussing yesterday I'm hesitant to keep creating packages until we have improved our release workflow.

Open to suggestions here, was just going with the path of least resistance to get something working.

Originally posted by @jessebraham in #847 (comment)