Combine normal and okay statuses.

- Changed all normal results to ok.
- Normal results were intended for tools that produced info and
  weren't expected to have problem results.
  - Ultimately not worth distinguishing from tools that sometimes
    show problems.
- One less color status makes the summary table simpler.
- Also changed the not-applicable status color to the lighter grey
  that normal used to have.
- Made the success status non-configurable since ok status is the
  only sensible status at the moment.

tests/worker_test.py

@@ -32,7 +32,7 @@ class WorkerTestCase(unittest.TestCase):
         worker_.process.stdin.write(f"{compression}\n".encode("utf-8"))
         future = worker_.run_tool("foo", tools.metadata)
         status = loop.run_until_complete(future)
-        self.assertEqual(status, tools.Status.normal)
+        self.assertEqual(status, tools.Status.ok)
         result_path = os.path.join(tools.CACHE_PATH, "foo-metadata")
         self.assertTrue(os.path.exists(result_path))