[PSM Interop] Add bootstrap generator test (#33833)

Based on https://github.com/grpc/grpc-go/pull/6463

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tools/internal_ci/linux/grpc_xds_k8s_lb.cfg

@@ -16,7 +16,7 @@
 
 # Location of the continuous shell script in repository.
 build_file: "grpc/tools/internal_ci/linux/grpc_xds_k8s_lb.sh"
-timeout_mins: 180
+timeout_mins: 240
 action {
   define_artifacts {
     regex: "artifacts/**/*sponge_log.xml"

tools/internal_ci/linux/grpc_xds_k8s_lb.sh

@@ -180,6 +180,9 @@ main() {
     "remove_neg_test"
     "round_robin_test"
   )
+  if [[ "${TESTING_VERSION}" =~ "master" ]]; then
+      test_suites+=('bootstrap_generator_test')
+  fi
   for test in "${test_suites[@]}"; do
     run_test $test || (( ++failed_tests ))
   done