Posting errors could be improved

[notgne2]

Every now and then one of these pops up serokell/deploy-rs#152 and can at times get quickly filled with many "similar" comments, meaning GitHub won't even show you what the latest error is. This also means by the time I can unsubscribe from the thread I now have multiple notifications instead of just one.

I think it would be better just to edit the issue message with whatever the current error is, rather than appending to an ever expanding list of errors. For PRs that become error-y, it can instead post a single error comment and update it (maybe post a new one if the last comment is by somebody else)

It also looks like error issues do not get closed out, as serokell/deploy-rs#187 still exists despite serokell/deploy-rs#189 now having been created.