Create collab branch for Clock Management RFC

[danieldegrasse]

For continued development of the clock management subsystem proposed in #72102, I would like to create a collaboration branch. Initially I expect @mathieuchopstm and I to engage here, but more vendors will likely do so as development continues.

The expected timeline for this branch is roughly 6 months- at that point we will clean up any wip commits on that branch, and prepare a PR for review against mainline Zephyr.

Branch name isn't too important to me, perhaps collab-clock-mgmt?