[CI] Enforce linting errors

Summary

Currently, our linting job allows failure. This was initially implemented in !76 (merged), and since we were doing a major refactor to the codebase we decided to allow failure here and just use the output for feedback along the way.

As the codebase becomes more stable and we get closer to general availability, it would be ideal to not allow failure here, thereby enforcing any problems that the linter finds to ensure the best code quality possible.

Acceptance criteria

• Failure is not allowed on the linting job
• .golangci.yml is tweaked as needed to give us helpful results