sg: add sg page to automate alerts creation
Created by: jhchabran
Port the script in https://github.com/sourcegraph/deploy-sourcegraph-cloud/pull/17235/files in sg
so we can use it in various places where we want to raise alerts, like failed deployments and others.
Part of https://github.com/sourcegraph/sourcegraph/issues/31854
Test plan
Tested in the other PR.