This updates the nightly workflow to run hourly as opposed to once
daily.

Notably, it also 
- changes the poll duration for the auto updater - we now poll 4 times
an hour on the Nightly channel and continue with the old rate for all
other channels
- moves the pre-checks to the linux runners, since we have more
resources available there
- only ever allow one concurrent nightly run

Release Notes:

- N/A