Summary:
Interrupt retryable syncback tasks that are taking too long so that we can
return control to the sync loop. The sync loop will retry the task later.
This diff adds a `forceReject` param to `interrupt()` so that we can return
control immediately instead of waiting for the current operation to finish
(for instance, the syncback task could be stuck in an imap operation, and a
normal interrupt would still have to wait for that to finish before returning
control to the callee)
Part of T7978
Test Plan: specs
Reviewers: evan, spang, mark, juan
Reviewed By: juan
Differential Revision: https://phab.nylas.com/D4269
