Import of testing in production binary

[ARR4N]

#3173 introduces a linter to catch leaking of test-only code into production. Most instances of testing imports can be excluded with build tags. This is a tracking issue to document the need for refactoring of the rest.

See: failing CI with removal of final workaround.

Resolution criteria

The workaround was to trick the linter's regex with //go:build test || !test to allow the PR to merge and this refactor to be tackled separately. All instances of said workaround have a TODO with this issue linked, and the issue SHOULD NOT be considered resolve until all are removed.

[github-actions]

This issue has become stale because it has been open 60 days with no activity. Adding the lifecycle/frozen label will cause this issue to ignore lifecycle events.