Add a rough "ProgressSink" for improved progress reporting flexibility
Summary: Ref T13396. This is very minimal, but bind "HTTPSFuture" to a more indirect/abstract progress reporting pathway than "PhutilConsoleProgressBar" provides.
Test Plan: In bin/host download, bound this new type of progress bar and got better-than-nothing console output.
Maniphest Tasks: T13396
Differential Revision: https://secure.phabricator.com/D20746