Implement Zicbop (prefetch.i, prefetch.r, prefetch.w)

[trdthg]

Why to implement this: see comment

There's no need to review it at the moment as it hasn't been tested yet(), just a reminder that someone is interested in it. (That's why I opened it as a draft)

Act only has tests for cbo.zero(from zicboz), so I'm trying to figure out the usage of act, riscof, ctg, isca ... and trying to add tests for zicbom and zicbop.