Update test framework: fix run_tests.py to support all test files, add auto-import-check for test files

node_modules/escalade/index.d.ts

@@ -0,0 +1,15 @@
+type Promisable<T> = T | Promise<T>;
+
+declare namespace escalade {
+	export type Callback = (
+		directory: string,
+		files: string[],
+	) => Promisable<string | false | void>;
+}
+
+declare function escalade(
+	directory: string,
+	callback: escalade.Callback,
+): Promise<string | void>;
+
+export = escalade;