Fingerprints broken when adding base classes in later phases

[nicolasstucki]

A quick fix for this issue is to disable them in Config.useFingerPrints.

We could consider removing them all completely as it seemed not to change the performance.

[nicolasstucki]

Executing the vulpix test suite 3 times with and without fingerprints there was not a noticeable difference it times. Gist with time logs.

[nicolasstucki]

@odersky @DarkDimius should we remove them? If so there there is a branch ready for a PR on staging. https://github.com/dotty-staging/dotty/tree/fix-%232417

[nicolasstucki]

Will be fixed by #2425.