[lldb][NFC] Remove FormatterChoiceCriterion

Summary:
The formatters code has a lot of 'reason' or 'why' values that we keep or-ing FormatterChoiceCriterion
enum values into. These values are only read by a single log statement and don't have any functional
purpose. It also seems the implementation is not finished (for example, display names and type
names don't have any dedicated enum values). Also everything is of course not tested or documented.

Let's just remove all of this.

Reviewers: labath, JDevlieghere, jingham, davide, vsk

Reviewed By: labath, vsk

Subscribers: JDevlieghere

Differential Revision: https://reviews.llvm.org/D77968