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/test-utils/client/src/lib.rs

@@ -184,7 +184,6 @@ impl<Block: BlockT, Executor, Backend, G: GenesisInit> TestClientBuilder<Block,
 		Executor: sc_client::CallExecutor<Block> + 'static,
 		Backend: sc_client_api::backend::Backend<Block>,
 	{
-
 		let storage = {
 			let mut storage = self.genesis_init.genesis_storage();