scheduler: Use heap to determine highest priority thread

kernel[/util]: Fix debug builds

kernel/util: Fixes in [MinMax]Heap implementation

kernel/util: Minor improvements in Heap and MinMaxHeap

* [MinMax]Heap::ModifyKey(): Do not attempt to move node if the key
actually hasn't changed.
* Allow allocating initial array at construction.

scheduler_affine: Use global core heap and per-core CPU heaps

There is a global heap of cores, where the key is the highest priority
of threads running on that core. Moreover, for each core there is
a heap of logical processors on this core where the key is the priority
of currently running thread.

The per-core heap is used for load balancing among logical processors
on that core. The global heap is used in initial decision where to put
the thread (note that the algorithm that makes this decision is not
complete yet).

kernel: Add support for SMP systems to simple scheduler

In SMP systems simple scheduler will be used only when all logical
processors share all levels of cache and the number of CPUs is low.
In such systems we do not have to care about cache affinity and
the contention on the lock protecting shared run queue is low. Single
run queue makes load balancing very simple.

kernel/util: Add heap implementation

scheduler: Use heap to determine highest priority thread

kernel[/util]: Fix debug builds

kernel/util: Fixes in [MinMax]Heap implementation

kernel/util: Minor improvements in Heap and MinMaxHeap

* [MinMax]Heap::ModifyKey(): Do not attempt to move node if the key
actually hasn't changed.
* Allow allocating initial array at construction.

scheduler_affine: Use global core heap and per-core CPU heaps

There is a global heap of cores, where the key is the highest priority
of threads running on that core. Moreover, for each core there is
a heap of logical processors on this core where the key is the priority
of currently running thread.

The per-core heap is used for load balancing among logical processors
on that core. The global heap is used in initial decision where to put
the thread (note that the algorithm that makes this decision is not
complete yet).

kernel: Add support for SMP systems to simple scheduler

In SMP systems simple scheduler will be used only when all logical
processors share all levels of cache and the number of CPUs is low.
In such systems we do not have to care about cache affinity and
the contention on the lock protecting shared run queue is low. Single
run queue makes load balancing very simple.

kernel/util: Add heap implementation