WASM runtime switch to import memory (#4737)

* WASM runtime switch to import memory

Up to now runtimes have exported their memory. To unify it with
sandboxing, this pr switches runtimes to import memory as well.

From a functional perspective, exporting/importing memory makes no
difference to the runtime.

To provide backwards compatibility, WASM exported memory is still supported.

* Revert debug stuff

* Revert some stuff

substrate/bin/node-template/runtime/build.rs

@@ -1,11 +1,10 @@
-use wasm_builder_runner::{build_current_project_with_rustflags, WasmBuilderSource};
+use wasm_builder_runner::WasmBuilder;
 
 fn main() {
-	build_current_project_with_rustflags(
-		"wasm_binary.rs",
-		WasmBuilderSource::Crates("1.0.9"),
-		// This instructs LLD to export __heap_base as a global variable, which is used by the
-		// external memory allocator.
-		"-Clink-arg=--export=__heap_base",
-	);
+	WasmBuilder::new()
+		.with_current_project()
+		.with_wasm_builder_from_crates("1.0.9")
+		.export_heap_base()
+		.import_memory()
+		.build()
 }