Enable tools_unittests and rtc_stats_unittests on iOS Simulator

The tests have been passing for some time, but were never added.

BUG=webrtc:5572, webrtc:5566
NOTRY=True

Review-Url: https://codereview.webrtc.org/2800813005
Cr-Commit-Position: refs/heads/master@{#17556}

tools-webrtc/ios/tests/common_tests.json

@@ -22,12 +22,18 @@
     {
       "app": "rtc_pc_unittests"
     },
+    {
+      "app": "rtc_stats_unittests"
+    },
     {
       "app": "system_wrappers_unittests"
     },
     {
       "app": "test_support_unittests"
     },
+    {
+      "app": "tools_unittests"
+    },
     {
       "app": "voice_engine_unittests"
     }