A customized TabLayout to be used as top navigation bar in leanback

Using viewpager instead of viewpager2 as there are some with focus flow
when DPAD_DOWN is pressed while focus is on tablayout. The focus does
not flow from the viewpager2/underlying recyclerview to the contents of
viewpager2.

Test: Unit test and added sample demo

Relnote: "Adding a customized TabLayout to be used as top navigation bar
in leanback"

Change-Id: I1e3048d300106ad0b0f9ef55f14e7070793a579a
diff --git a/settings.gradle b/settings.gradle
index b96fabe..62217d8 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -203,6 +203,7 @@
 includeProject(":leanback:leanback", "leanback/leanback")
 includeProject(":leanback:leanback-paging", "leanback/leanback-paging")
 includeProject(":leanback:leanback-preference", "leanback/leanback-preference")
+includeProject(":leanback:leanback-tab", "leanback/leanback-tab")
 includeProject(":lifecycle:integration-tests:incrementality", "lifecycle/integration-tests/incrementality")
 includeProject(":lifecycle:integration-tests:lifecycle-testapp", "lifecycle/integration-tests/testapp")
 includeProject(":lifecycle:integration-tests:lifecycle-testapp-kotlin", "lifecycle/integration-tests/kotlintestapp")