test-runtime: json_patch dep removed (#3062)

We don't need dependency on `json_patch` there is implementation of
needed function in `sc_chain_spec` crate.
This PR makes this function publicly available and removes the dep.

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

@@ -1410,7 +1410,7 @@ mod tests {
 				}
 			});
 
-			json_patch::merge(&mut default_config, &patch);
+			sc_chain_spec::json_merge(&mut default_config, patch);
 
 			// Build genesis config using custom json:
 			let mut t = BasicExternalities::new_empty();