Packit-service: copr builds: create a comment instead of setting a status

[TomasTomecek]

if there is an error during execution, we set status on the PR with description from the exception: github doesn't allow us to put there too much text; we should instead create a comment on the PR and include the text inside while setting status to something short, e.g. "There was an error during the build process".

[msehnout]

Example:

See the title in the div and compare it with what you can actually see in the status.

[jpopelka]

Could we as a start just remove the "There was an error while running the build:"?
We already know that because there's the red cross, so we could just put the actual reason there.