Conflict-less feature flags

Whenever one creates a merge request which contains modifications to feature flags, one can be almost certain that it will eventually conflict because somebody else has also modified feature flags. And because they're colocated in a single spot, the chance for conflicts is extremely high. While the conflicts are almost always trivial, it still gets annoying after some time.

This MR addresses this issue by splitting up feature flags into their own files. Furthermore, it introduces a new constructor for feature flags which knows to append to the All array such that we don't have to manually keep track of all feature flags anymore.