score: PR2136: Fix _Thread_Change_priority()

Add call to _Scheduler_Schedule() in missing path after
_Thread_Set_transient() in _Thread_Change_priority().  See also
sptests/spintrcritical19.

Add thread parameter to _Scheduler_Schedule().  This parameter is
currently unused but may be used in future SMP schedulers.

Do heir selection in _Scheduler_Schedule().  Use
_Scheduler_Update_heir() for this in the particular scheduler
implementation.

Add and use _Scheduler_Generic_block().
score: Add _Scheduler_priority_Get_scheduler_info

Add and use _Scheduler_priority_Get_scheduler_info().
score: Add _Scheduler_priority_Get_ready_queues()

Add and use _Scheduler_priority_Get_ready_queues()
score: _Scheduler_priority_Ready_queue_first()

Remove superfluous check since a ready thread must exist.
score: _Scheduler_priority_Ready_queue_initialize()

Move workspace allocation to _Scheduler_priority_Initialize().
score: _Priority_bit_map_Handler_initialization()

Delete _Priority_bit_map_Handler_initialization() and rely on BSS
initialization.  Move definition of _Priority_Major_bit_map and
_Priority_Bit_map to separate file.  Move definition of __log2table also
to this file.
score: Add _Priority_bit_map_Is_empty()
smp: Replace Scheduler_simple_smp_Control

Replace Scheduler_simple_smp_Control with Scheduler_SMP_Control.  Rename
_Scheduler_simple_smp_Instance() to _Scheduler_SMP_Instance().
smp: Rename _Scheduler_simple_smp_Start_idle()

Rename _Scheduler_simple_smp_Start_idle() to
_Scheduler_SMP_Start_idle().
smp: _Scheduler_simple_smp_Allocate_processor()

Rename _Scheduler_simple_smp_Allocate_processor() to
_Scheduler_SMP_Allocate_processor().
smp: Optimize Simple SMP scheduler

Add Thread_Control::is_in_the_air field if configured for SMP.  This
helps to simplify the extract operation and avoids superfluous
inter-processor interrupts.  Move the processor allocation step into the
enqueue operation.

Add and use _Scheduler_simple_smp_Get_highest_ready().  Add and use
_Scheduler_SMP_Get_lowest_scheduled().
smp: Generalize Simple SMP scheduler
smp: Add Deterministic Priority SMP Scheduler