Package release before publishing (#42218)

* Package separately to publish

* Fix interpolation

* Windows format envvars

* More descriptive msg

* Won't publish from here

* Resolve docker issues in PR build

* Rename package docker step

* Correct npm release JSON structure

scripts/build/retrieve-npm-packages.sh

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+set -e
+
+GRAFANA_TAG=${1:-}
+
+if echo "$GRAFANA_TAG" | grep -q "^v"; then
+	_grafana_version=$(echo "${GRAFANA_TAG}" | cut -d "v" -f 2)
+else
+  echo "Provided tag is not a version tag, skipping packages release..."
+	exit
+fi
+
+echo "Retrieving prerelease NPM artifacts"
+ZIPFILE=grafana-npm-${_grafana_version}.tgz
+
+echo "${GCP_KEY}" | base64 -d > credentials.json
+gcloud auth activate-service-account --key-file=credentials.json
+gsutil cp "gs://${PRERELEASE_BUCKET}/artifacts/npm/$ZIPFILE" "$ZIPFILE"
+tar -xzf "$ZIPFILE"