Move chunk generation and provider response handling to a dedicated work queue. (#283)
Move chunk generation and provider response handling to a dedicated work queue. (#283)

Move chunk generation and provider response handling to a dedicated work queue.

The `chunkWorkQueue` is a serial queue targeting, for now, the default global queue. Creation of chunk data and any file I/O that takes place as a result will now take place on this queue, rather than often being on the main queue.

google/gtm-session-fetcher,thomasvl/gtm-session-fetcher,google/gtm-session-fetcher,thomasvl/gtm-session-fetcher,thomasvl/gtm-session-fetcher,google/gtm-session-fetcher