CI does not catch conflicts in go.sum files

[pysel]

Background

CI can pass even if there are conflicts in go.sum files (note: it won't pass if there is a conflict in go.mod file). It can lead to potential merge with conflicts to main. Example: #6492 (comment) (at the time of writing, the comment is not outdated and CI is green).

Suggested Design

CI should catch these merge conflicts and block merge before they are resolved

Acceptance Criteria

CI catches merge conflicts in go.sum files (would be also nice to make sure that every other file is also checked, what if go.sums are not the only files?)