Remove fingerprint parameter

We have two quite similar parameters: lookup and fingerprint. Both expect a full hex fingerprint and return a single relay or bridge (or more than just one when we implement #25448 (moved)).

The main difference between these two parameters is that fingerprint returns relays or bridges regardless of whether they have been running in the past week. There is no other way to access these documents other than by knowing the exact fingerprint of a relay or hashed fingerprint of a bridge. Unlike other parameters, the fingerprint does not even work with hashed relay fingerprints or hashed hashed bridge fingerprints.

Do we need to keep the fingerprint parameter with this somewhat special behavior?

We added the parameter four years ago for one of the EFF relay challenges. But is it still in use? And is that because clients really need to access older relays and bridges, or because their developers did not know about the lookup parameter?

Setting type to enhancement, because removing the fingerprint parameter would let us remove some special code from the code base.

However, if there are valid use cases to keep the fingerprint parameter, let's just collect them here and let the parameter in.