Summary:
Removed loadGKs and loadDistilleryGKs from the `flipper` API, as it leaked implementation details of GK that didn't work well with decapitation later in this diff, and refactored it to using `getFlipperLib().GK`.
After that discovered that those APIs are actuallly only used by nt-shared's performGKcheck, which was already removed from all usages in D27736036, so just removed the code altogether. But left loading distillery GKs in place, since that is good infra structure to provide anyway(?), although we don't have active use cases atm
Reviewed By: jknoxville
Differential Revision: D32529600
fbshipit-source-id: a03fb14ada21018d329eea78a59f1b20610b2fd3
d48f22b8dc