Split getAppSearchImpl and createAppSearchImpl in AppSearchImpl

User could never call an uninitialized SearchSession, so convert and
propagate the initialize error in getAppSearchImpl to user
for every call is unnecessary.

Test: presubmit
Bug: 162450968
Change-Id: Ie2b3c7c0a56852d7e517c616960c19b7b9e9ad35
diff --git a/apex/appsearch/testing/Android.bp b/apex/appsearch/testing/Android.bp
index eb072af..3c5082e 100644
--- a/apex/appsearch/testing/Android.bp
+++ b/apex/appsearch/testing/Android.bp
@@ -30,5 +30,8 @@
         "guava",
         "truth-prebuilt",
     ],
-    visibility: ["//cts/tests/appsearch"],
+    visibility: [
+        "//cts/tests/appsearch",
+        "//vendor:__subpackages__",
+    ],
 }