The previous cache manager support used a single souce file
(cache_manager.c) which included an implementation header (cache_.h).
This required the use of specialized include paths to find the right
header file. Change this to include a generic implementation header
(cacheimpl.h) in specialized source files.
Use the following directories and files:
* bsps/shared/cache
* bsps/@RTEMS_CPU@/shared/cache
* bsps/@RTEMS_CPU@/@RTEMS_BSP_FAMILY/start/cache.c
Update #3285.
