[PSM Interop] Configure CODEOWNERS (#35254)

Configures CODEOWNERS for the PSM Interop framework
`/tools/run_tests/xds_k8s_test_driver/` to be @sergiitk, @XuanWang-Amos,
@gnossen.

We need this change to be able to prevent unexpected changes to the the
framework while it's being moved to the dedicated grpc/psm-interop repo.

.github/CODEOWNERS

@@ -10,3 +10,4 @@
 /src/core/lib/resolver/** @markdroth
 /src/core/lib/service_config/** @markdroth
 /tools/dockerfile/** @jtattermusch @apolcyn
+/tools/run_tests/xds_k8s_test_driver/** @sergiitk @XuanWang-Amos @gnossen