ci: improve Go tests output
Created by: jhchabran
Partly covers https://github.com/sourcegraph/sourcegraph/issues/30115
This PR improves the output for Go tests by:
- adding color, failed will be in red which is easier to spot.
- force folding of CodeCov which is creating noise for nothing
- force expand the output of Go tests so they are immediately visible.
Test plan
- Inspected manually the output of a green build
- Triggered a failure and made sure the command was still working by failing the build step
- Checked that the analytics are still reported.