coreos-download: add GCP info on cloud launchable tab
Adds GCP cloud launchable name, family and project on the download
page. This works along side with
- https://github.com/coreos/fedora-coreos-releng-automation/pull/112 to add GCP info in release.json
- https://github.com/coreos/fedora-coreos-stream-generator/pull/11 to add GCP info in ${stream}.json
This change reads metadata from ${stream}.json and renders it. It is also possible to read directly
from individual meta.json file but since the download page is already utilizing ${stream}.json, this
changes is trying to make use of already fetched metadata instead of fetching another meta.json.
Closes: https://github.com/coreos/fedora-coreos-tracker/issues/494
Signed-off-by: Allen Bai <abai@redhat.com>