Add emulator_images_%s filegroups for Bazel Android devices.

A previous change added this filegroup with the name %s_files. Recent discussions have suggested changing the naming convention to be a prefix instead before it is too late.

--
PiperOrigin-RevId: 150117207
MOS_MIGRATED_REVID=150117207
diff --git a/tools/android/android_sdk_repository_template.bzl b/tools/android/android_sdk_repository_template.bzl
index d6a29f8..200fe28 100644
--- a/tools/android/android_sdk_repository_template.bzl
+++ b/tools/android/android_sdk_repository_template.bzl
@@ -215,7 +215,14 @@
   for system_image_dir in system_image_dirs:
     name = "_".join(system_image_dir.split("/")[1:])
 
+    # TODO(ajmichael): Remove this target after unified_launcher's tests are
+    # updated to use the emulator_images_%s filegroups instead.
     native.filegroup(
         name = "%s_files" % name,
         srcs = native.glob(["%s/**" % system_image_dir]),
     )
+
+    native.filegroup(
+        name = "emulator_images_%s" % name,
+        srcs = native.glob(["%s/**" % system_image_dir]),
+    )