Use assert in wapp_mem_util_align_forward instead of returning NULL

src/core/os/mem/mem_os.h

@@ -14,7 +14,6 @@
 #error "Unrecognised platform"
 #endif
 
-void *wapp_mem_util_align_forward(void *ptr, u64 alignment);
 void *wapp_mem_util_alloc(void *addr, u64 size, MemAccess access, MemAllocFlags flags, MemInitType type);
 void wapp_mem_util_free(void *ptr, u64 size);