[otbn,sim] KMAC RTL co-simulation support plan

### Description

Commit 16e4d284 mentions KMAC interface is "only supported for
standalone simulator use" and "not yet possible to do a RTL
co-simulation."

Is there a rough timeline for when KMAC co_sim will be supported?
We've been looking into using it and would find it helpful for
verification.

Thanks!

Start by reading commit 16e4d284 and the current KMAC standalone simulator support. Determine what RTL co-simulation support would require and establish whether a timeline can be defined; the issue does not name specific files or tests, so the completion criteria need clarification.

Written by the indexing model from the issue text.