Create a testutils module to share common testing code.

First module to move there is PollingCheck.java.

Bug: 36139124
Test: ./gradlew assembleAndroidTest works
Change-Id: Ic2626b8cd79475fa79af39b8eefddba41a9ecb91

diff --git a/settings.gradle b/settings.gradle
index ce8ead0..b6c8b40 100644
--- a/settings.gradle
+++ b/settings.gradle

@@ -152,6 +152,15 @@
 
 /////////////////////////////
 //
+// Testing libraries
+//
+/////////////////////////////
+
+include ':support-testutils'
+project(':support-testutils').projectDir = new File(rootDir, 'testutils')
+
+/////////////////////////////
+//
 // External
 //
 /////////////////////////////