Rename TEST_* to ANDROIDX_TEST_*

Renaming unclear naming prefix in our test deps to show that certain
deps are only useful in Android instrumented tests. Also, clean up a
bunch of unused test deps that were probably copied in due to the
confusing naming.

Test: ./gradlew test && ./gradlew cC
Change-Id: I4b9e3e73c2c115d3c8359871e481e5e8fef8a544
diff --git a/dumb-tests/build.gradle b/dumb-tests/build.gradle
index c541388..3fbd3e4 100644
--- a/dumb-tests/build.gradle
+++ b/dumb-tests/build.gradle
@@ -23,10 +23,10 @@
 
 dependencies {
     testImplementation(JUNIT)
-    androidTestImplementation(TEST_EXT_JUNIT)
-    androidTestImplementation(TEST_CORE)
-    androidTestImplementation(TEST_RUNNER)
-    androidTestImplementation(TEST_RULES)
+    androidTestImplementation(ANDROIDX_TEST_EXT_JUNIT)
+    androidTestImplementation(ANDROIDX_TEST_CORE)
+    androidTestImplementation(ANDROIDX_TEST_RUNNER)
+    androidTestImplementation(ANDROIDX_TEST_RULES)
 }
 
 tasks['check'].dependsOn(tasks['connectedCheck'])