🏨 Switch Android gtests to use generated wrapper scripts

scripts/slave/recipe_modules/chromium_android/example.expected/tester_with_step_warning.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "\nimport os, sys\n\nbuild_path = sys.argv[1]\nif os.path.exists(build_path):\n  for (path, dir, files) in os.walk(build_path):\n    for cur_file in files:\n      if cur_file.endswith('index.lock'):\n        path_to_file = os.path.join(path, cur_file)\n        print 'deleting %s' % path_to_file\n        os.remove(path_to_file)\n",
       "[SLAVE_BUILD]"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "cleanup index.lock",
@@ skipping 567 matching lines @@
     "cwd": "[SLAVE_BUILD]",
     "env": {
       "CHROMIUM_OUTPUT_DIR": "[SLAVE_BUILD]/src/out/Release"
     },
     "name": "Instrumentation test SmallTest"
   },
   {
     "cmd": [
       "python",
       "-u",
-      "[SLAVE_BUILD]/src/build/android/test_runner.py",
-      "gtest",
-      "-s",
-      "unittests",
+      "[SLAVE_BUILD]/src/out/Release/bin/run_unittests",
       "--blacklist-file",
       "[SLAVE_BUILD]/src/out/bad_devices.json",
       "--verbose",
-      "--release",
       "--isolate_file_path=[SLAVE_BUILD]/src/some_file.isolate",
       "--gtest_filter=WebRtc*",
       "--tool=asan"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
-      "CHROMIUM_OUTPUT_DIR": "[SLAVE_BUILD]/src/out/Release",
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "unittests",
     "~followup_annotations": [
       "step returned non-zero exit code: 88",
       "@@@STEP_WARNINGS@@@"
     ]
   },
   {
     "name": "$result",
     "reason": "Warning: Step('unittests') returned 88",
     "status_code": 88
   }
 ]