Use CLI to configure max instances cache (#5177)

* Use CLI to configure max instances cache

* Fix tests

* Move default value into CLI

* Use SmallVec

* Apply review comments

* Get rid of `SmallVec`

Co-authored-by: Bastian Köcher <git@kchr.de>

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

@@ -244,7 +244,7 @@ impl<Block: BlockT, E, Backend, G: GenesisInit> TestClientBuilder<
 		Backend: sc_client_api::backend::Backend<Block> + 'static,
 	{
 		let executor = executor.into().unwrap_or_else(||
-			NativeExecutor::new(WasmExecutionMethod::Interpreted, None)
+			NativeExecutor::new(WasmExecutionMethod::Interpreted, None, 8)
 		);
 		let executor = LocalCallExecutor::new(self.backend.clone(), executor);