Summary:
This change isolates the usage of folly async from Flipper. Is now self-contained in Flipper Folly schedulers.
Users of Flipper can decide not to use the types defined in that header and implement their own.
NOTE: changes are minimal, we are just replacing direct calls to folly event base with a scheduler which simply relays this on to folly.
Reviewed By: fabiomassimo
Differential Revision: D36626483
fbshipit-source-id: add0241caf4af0aa5c3b5c2e7efc2e725f5400ab
e44cad5e99