Generate Android.bp files; Convert to Android.bp

Keep generating Android.mk files for java libraries, but move c++ shared
libraries to Android.bp.

Now that we're building these in Soong, we can build hidl_test in Soong
as well.

Bug: 31742855
Test: hardware/interfaces/update-makefiles.sh
Change-Id: Ifd7b6d423971b04b2120b51d63eacfc6b162e25d
diff --git a/Android.bp b/Android.bp
index eb0bcfb..ad0e933 100644
--- a/Android.bp
+++ b/Android.bp
@@ -14,6 +14,7 @@
 
 subdirs = [
     "c2hal",
+    "test",
     "utils",
 ]