[lib][heap] have novm initialize itself, rename novm 'heap' to 'arena' to be less confusing

top/main.c

@@ -103,10 +103,6 @@ void lk_main(ulong arg0, ulong arg1, ulong arg2, ulong arg3)
 	dprintf(INFO, "boot args 0x%lx 0x%lx 0x%lx 0x%lx\n",
 		lk_boot_args[0], lk_boot_args[1], lk_boot_args[2], lk_boot_args[3]);
 
-#if !WITH_KERNEL_VM
-	novm_init();
-#endif
-
 	// bring up the kernel heap
 	dprintf(SPEW, "initializing heap\n");
 	lk_primary_cpu_init_level(LK_INIT_LEVEL_TARGET_EARLY, LK_INIT_LEVEL_HEAP - 1);