Public animation library unit tests - add manifest and test activity

The changes needed to allow running the tests in precommit

Test: atest
Bug: 271850966
Change-Id: Idb042eecc9be0e12085642c7c012a05350eb45a4
diff --git a/animationlib/Android.bp b/animationlib/Android.bp
index dd0ac1e..d67a5de 100644
--- a/animationlib/Android.bp
+++ b/animationlib/Android.bp
@@ -39,6 +39,7 @@
 
 android_test {
     name: "animationlib_tests",
+    manifest: "tests/AndroidManifest.xml",
 
     static_libs: [
         "animationlib",