actions: simplify usage of Matchable

This removes use of the pseudo-internal toString() function and also
removes extraneous uses of ReturnType<>. Also, a new when() method
is added to simplify additional uses.

src/fileStorage/sagas.test.ts

@@ -82,7 +82,7 @@ it('should dispatch fail action if file does not exist', async () => {
     saga.put(fileStorageReadFile(testFileName));
 
     action = await saga.take();
-    expect(action).toHaveProperty('type', fileStorageDidFailToReadFile.toString());
+    expect(fileStorageDidFailToReadFile.matches(action)).toBeTruthy();
 
     await saga.end();
 });