k8s.sgdev: set up LSIF uploads for Sourcegraph repositories

Created by: bobheadxi

Code intel uploads currently only go to Sourcegraph.com: https://github.com/sourcegraph/sourcegraph/blob/main/.github/workflows/lsif.yml

To encourage dogfooding on k8s.sgdev, we'll want to ensure that these uploads are going to k8s.sgdev.org as well

We should also do a pass to see if there are private repos we can index and upload (and ensure they are available)

We should also update handbook documentation for how to set up uploads to the dogfood instance