eden: split the remaining of timeGenerator
eden: split the remaining of timeGenerator

Summary:
In a future diff, Watchman will query EdenFS via a streaming API, to make it
easier to do that, let's split the code a bit.

Reviewed By: kmancini

Differential Revision: D35916441

fbshipit-source-id: 7dae14bd0ab97756099c79ad32d68c5f1e196429

facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman