* ci: Use Github artifacts for PRs
This PR extends the build job by upload artifacts for all PRs.
The version of those builds is set to "1.0.0-<git_short_hash>" and those
builds have the updater explicitly disabled.
With this in place, we will be able to disable ApppVeyor on PRs.
* Add actions to comment build links
As Github doesn't provide links to unlogged users, we use nightly.link for that.
* Address Ac_k's comments
