[WUD-2880] Allow multiple future waiting and unwrapping

[mhidalgo-rai]

Proposed changes

This patch updates wait_for_future() and unwrap_future() to accept multiple futures at a time, modeled after concurrent.futures.wait() and concurrent.futures.as_completed().

Checklist

• Lint and unit tests pass locally
• I have added tests that prove my changes are effective
• I have added necessary documentation to communicate the changes

Additional comments

[jbarry-bdai]

Admittedly not 100% sure about all the code but this looks about right!

[mhidalgo-rai]

Making logging tests as flaky so we can unblock this. It honestly looks like delayed pub/sub discovery or message drop triggered by middleware state left behind from one test to the next. It's gotten worse recently. Fallout from the latest Humble sync perhaps.