Add test target to f/b/packages/overlays.

- Added IconPackOverlayTest to ensure that there icon pack overlays do not
get out of sync with the underlying drawables in each apk.
- Remove overlayable_icons_test.xml from each app since this test makes
them no longer necessary
- Add apcts target OverlayTests.apk - TODO add this to presubmit config
for settings and systemui

Bug: 134566901
Test: atest IconPackOverlayTest
Change-Id: I99243db4839ac41dad01abf9f83ebda757dbbb77
diff --git a/packages/overlays/tests/Android.bp b/packages/overlays/tests/Android.bp
new file mode 100644
index 0000000..343367a
--- /dev/null
+++ b/packages/overlays/tests/Android.bp
@@ -0,0 +1,37 @@
+// Copyright (C) 2019 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+android_test {
+    name: "OverlayTests",
+
+    certificate: "platform",
+
+    srcs: ["src/**/*.java"],
+
+    libs: [
+        "android.test.runner",
+        "android.test.base",
+    ],
+
+    platform_apis: true,
+
+    static_libs: [
+        "androidx.test.rules",
+        "androidx.test.espresso.core",
+        "mockito-target-minus-junit4",
+        "truth-prebuilt",
+    ],
+
+    dxflags: ["--multi-dex"],
+}