Migrate existing navigation-testing to internal testutils

The existing navigation-testing files are used for internal testing of
the navigation library. This change migrates this existing module to the
internal testutils module in order to free up the navigation-testing
module for a new navigation testing library.

Test: ./gradlew bOS
Change-Id: Ie5054bfcf6b3053b28446174d302587403d2468a
diff --git a/navigation/navigation-runtime/build.gradle b/navigation/navigation-runtime/build.gradle
index b2ad1c3..3ca981d 100644
--- a/navigation/navigation-runtime/build.gradle
+++ b/navigation/navigation-runtime/build.gradle
@@ -33,7 +33,7 @@
     api("androidx.savedstate:savedstate:1.0.0")
     api(project(":lifecycle:lifecycle-viewmodel-savedstate"))
 
-    androidTestImplementation(project(":navigation:navigation-testing"))
+    androidTestImplementation(project(":internal-testutils-navigation"))
     androidTestImplementation(ANDROIDX_TEST_EXT_JUNIT)
     androidTestImplementation(ANDROIDX_TEST_CORE)
     androidTestImplementation(ANDROIDX_TEST_RUNNER)