Ability to enable/disable `may_race` checks per race digest

[michael-schwarz]

Such options are needed to make experiments to see how relevant what digest is for our new project.

[michael-schwarz]

We have decided that this feature is not useful to maintain in Goblint. With the paper now accepted, I will close this. I'll keep #1666 open in case the artifact reviewers suggest changes we want to incorporate into a final version of the artifact.