Enable Gitaly custom linters
This MR enables gitaly-linters, which is a custom linter tailored for Gitaly. It was added in Add golangci-lint custom linter infrastructure (!5398 - merged). As a result, we need to fix all the offenses of two categories:
- Manually quoting with
"%s"
and'%s'
. Replace occurrences by%q
. - Wrong error wrapping verb. Replace occurrences by
%w
.