Upgrade/patch/replace Go build image

[erikgb]

What

The image used to build the operator binary seems to be a Cybozu Ubuntu Jammy based image:

accurate/Dockerfile

Line 2 in ad5cd95

FROM quay.io/cybozu/golang:1.20-jammy as builder

Is there any particular reason for not using the official Go image, https://hub.docker.com/_/golang?

How

Replace the Go binary build image with golang:1.21, eventually an exact image digest if we want reproducible builds.

Checklist

• Finish implementation of the issue
• Test all functions
• Have enough logs to trace activities
• Notify developers of necessary actions

[zoetrope]

I've upgraded to go1.21 for now. #105

While I'm using quay.io/cybozu/golang in accordance with our company policy, I believe we could also use the official golang if needed.

[erikgb]

While I'm using quay.io/cybozu/golang in accordance with our company policy, I believe we could also use the official golang if needed.

We would prefer a more open/neutral base image. Is the current base image open-sourced?

[yamatcha]

Base image is built in this open-source repository.
https://github.com/cybozu/neco-containers/tree/main/golang-all