Actually add the xds interop script

packages/grpc-js/scripts/xds.sh

@@ -0,0 +1,44 @@
+#!/bin/bash
+
+nvm use 12
+
+set -exu -o pipefail
+[[ -f /VERSION ]] && cat /VERSION
+
+cd $(dirname $0)
+cd ..
+base=$(pwd)
+npm run compile
+
+cd ../../..
+branch=$(git branch --all --no-color --contains "${KOKORO_GITHUB_COMMIT}" \
+    | grep -v HEAD | head -1)
+shopt -s extglob
+branch="${branch//[[:space:]]}"
+branch="${branch##remotes/origin/}"
+shopt -u extglob
+
+git clone -b "${branch}" --single-branch --depth=1 https://github.com/grpc/grpc.git
+
+grpc/tools/run_tests/helper_scripts/prep_xds.sh
+
+# Test cases "path_matching" and "header_matching" are not included in "all",
+# because not all interop clients in all languages support these new tests.
+#
+# TODO: remove "path_matching" and "header_matching" from --test_case after
+# they are added into "all".
+GRPC_TRACE=xds_client,round_robin,resolving_load_balancer GRPC_VERBOSITY=DEBUG \
+  python3 grpc/tools/run_tests/run_xds_tests.py \
+    --test_case="all" \
+    --project_id=grpc-testing \
+    --source_image=projects/grpc-testing/global/images/xds-test-server-2 \
+    --path_to_server_binary=/java_server/grpc-java/interop-testing/build/install/grpc-interop-testing/bin/xds-test-server \
+    --gcp_suffix=$(date '+%s') \
+    --verbose \
+    --client_cmd="node grpc-node/packages/grpc-js/build/interop/xds-interop-client \
+      --server=xds:///{server_uri} \
+      --stats_port={stats_port} \
+      --qps={qps} \
+      {fail_on_failed_rpc} \
+      {rpcs_to_send} \
+      {metadata_to_send}"