kernel: remove some kernel objects from tracking

These are removed as the APIs that use them are not suitable for
exporting to userspace.

- Kernel workqueues run in supervisor mode, so it would not be
appropriate to allow user threads to submit work to them. A future
enhancement may extend or introduce parallel API where the workqueue
threads may run in user mode (or leave as an exercise to the user).

- Kernel slabs store private bookkeeping data inside the
user-accessible slab buffers themselves. Alternate APIs are planned
here for managing slabs of kernel objects, implemented within the
runtime library and not the kernel.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>

include/kernel.h

@@ -133,8 +133,6 @@ struct k_mem_partition;
 enum k_objects {
 	/* Core kernel objects */
 	K_OBJ_ALERT,
-	K_OBJ_DELAYED_WORK,
-	K_OBJ_MEM_SLAB,
 	K_OBJ_MSGQ,
 	K_OBJ_MUTEX,
 	K_OBJ_PIPE,
@@ -142,8 +140,6 @@ enum k_objects {
 	K_OBJ_STACK,
 	K_OBJ_THREAD,
 	K_OBJ_TIMER,
-	K_OBJ_WORK,
-	K_OBJ_WORK_Q,
 
 	/* Driver subsystems */
 	K_OBJ_DRIVER_ADC,