The work area initialization was done by the BSP through
bsp_work_area_initialize(). This approach predated the system
initialization through the system initialization linker set. The
workspace and C program heap were unconditionally initialized. The aim
is to support RTEMS application configurations which do not need the
workspace and C program heap. In these configurations, the workspace
and C prgram heap should not get initialized.
Change all bsp_work_area_initialize() to implement _Memory_Get()
instead. Move the dirty memory, sbrk(), per-CPU data, workspace, and
malloc() heap initialization into separate system initialization steps.
This makes it also easier to test the individual initialization steps.
This change adds a dependency to _Heap_Extend() to all BSPs. This
dependency will be removed in a follow up change.
Update #3838.
