Restore per font oversampling override.

[bruvzg]

Fixes #107706

Restores part of functionality removed when reworking oversampling system, I missed some use case and unlike global oversampling, this override is still useful and not directly replaced by new system.

[Mickeon]

I'll come back to this when rebasing #107536. Either way the descriptions are okay now, and indeed a feature went missing along the way.

[Repiteo]

Thanks!