bluetooth: controller: Revised ticker for improved conflict resolution

Changed ticker behavior to resolve conflicts in ticker_worker instead of
in ticker_job. This allows better real-time slot allocation, as well as
allowing callbacks even if ticker node doesn't get air-time (for audio
stream housekeeping). A priority property now also allows prioritizing
one ticker node over others.
Compatibility mode enables lagacy ticker behavior if needed.

Signed-off-by: Morten Priess <mtpr@oticon.com>