kernel: Make the k_heap backend default for k_mem_pool

Legacy code can switch back to the original implementation where it
needs it, but we don't want new code to be unintentionally dependent
on the behavior of the older allocator.  The new one is a better
general purpose choice.

Signed-off-by: Andy Ross <[email protected]>

Author: Andy Ross

kernel/Kconfig

@@ -467,6 +467,7 @@ config NUM_PIPE_ASYNC_MSGS
 
 config MEM_POOL_HEAP_BACKEND
 	bool "Use k_heap as the backend for k_mem_pool"
+	default y
 	help
 	  This selects a backend implementation for k_mem_pool based
 	  on the sys_heap abstraction instead of the legacy