sched: Migrate sched to use new tick dependency mask model

Instead of providing asynchronous checks for the nohz subsystem to verify
sched tick dependency, migrate sched to the new mask.

Everytime a task is enqueued or dequeued, we evaluate the state of the
tick dependency on top of the policy of the tasks in the runqueue, by
order of priority:

SCHED_DEADLINE: Need the tick in order to periodically check for runtime
SCHED_FIFO    : Don't need the tick (no round-robin)
SCHED_RR      : Need the tick if more than 1 task of the same priority
                for round robin (simplified with checking if more than
                one SCHED_RR task no matter what priority).
SCHED_NORMAL  : Need the tick if more than 1 task for round-robin.

We could optimize that further with one flag per sched policy on the tick
dependency mask and perform only the checks relevant to the policy
concerned by an enqueue/dequeue operation.

Since the checks aren't based on the current task anymore, we could get
rid of the task switch hook but it's still needed for posix cpu
timers.

Reviewed-by: Chris Metcalf <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Luiz Capitulino <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Viresh Kumar <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>

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