[FR] Formally deprecate gcr.io/cloud-builders/go

## Detailed Feature Information

**Which builder is relevant to this request?**

gcr.io/cloud-builders/go

**Is your feature request related to a problem? Please describe.**

Yes, the latest go builder image available is 1.22, which is unsupported since 2025-02-04. It should not be used to build anything due to CVEs.

The current version of golang is 1.25.3 and the oldest supported minor version is 1.24.9, so the cloud-builders images are 2-3 versions behind.

**Describe the solution you'd like**

Formally deprecate `gcr.io/cloud-builders/go` images and recommend the use of the [official golang image](https://hub.docker.com/_/golang) from Docker Hub.

- GCP's own docs for [Build and test Go applications](https://cloud.google.com/build/docs/building/build-go) use the official golang image.
- Having these obsolete / insecure images around only contributes to confusion and security issues in the ecosystem.
- Endlessly building these images also wastes resources if they provide no value beyond the official image.

**Describe alternatives you've considered**

Update the script to build the current supported versions and remove the old unsupported versions.

However, there were attempts to update the version to 1.23 a year ago in #1029, but there was no response.