executors: deploy on k8s

[davejrt]

This is my interpretation of https://github.com/sourcegraph/sourcegraph/issues/42469

It's a WIP as there is no documentation but we need an artefact for folks to deploy as well, and before I can document the process, we need to agree on what that is.

Right now this creates a single replica, with yet to be determined resource requirements. It deploys a docker in docker sidecar to avoid exposing the underlying container runtime on the k8s host. It also deploys a pull through cache to avoid docker rate limiting.

Assuming this is good, further steps are to ensure this works with kustomize/helm and is documented with a readme and exisiting executor docs are amended.

Edit: @eseliger this was tested on k8s 1.24 with containerd as the underlying runtime. Given we are exposing docker in docker to this, we don't have any compatibility problems in the short/medium term whilst we potentially move away from calling docker directly.

Checklist

• CHANGELOG.md updated
• K8s Upgrade notes updated
• Sister deploy-sourcegraph-docker change:
• All images have a valid tag and SHA256 sum

Test plan

Tested running a SSBC on S2

[eseliger]

this looks pretty solid to me :)

[eseliger]

using a separate docker daemon actually seems really smart to work around the issues, great idea!