[sestarnix] Use test_type="gtest" for userspace test components

Use the "gtest" test type, so that the test framework will
integrate properly for test listing, filtering, etc.

Change-Id: I22b0ff9b97e8f76e9154003c944db7b6933037df
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1235108
Fuchsia-Auto-Submit: Wez <[email protected]>
Commit-Queue: Auto-Submit <[email protected]>
Reviewed-by: Ambre Williams <[email protected]>

Author: drwez

src/starnix/tests/selinux/userspace/meta/sestarnix_userspace_test.shard.cml

@@ -8,6 +8,7 @@
     ],
     program: {
         runner: "starnix_test_runner",
+        test_type: "gtest",
     },
     children: [
         {