core: Reworked the cycle timers

core: Reworked the cycle timers

Ensure that a timer when called does not continue to have a
"call next" that is smaller than the current cycle, bogging
down the rest of the core.
Also ensure the cycle is always incremented by at least one
when sleeping, even if a cycle callback is called.

Signed-off-by: Michel Pollet <buserror@gmail.com>