Origin trials process reminder scripts need to be updated for the Chrome 2-week release schedule

[ot_process_reminders.py](https://github.com/GoogleChrome/chromium-dashboard/blob/d0d21c81719803cdc7ad39ae88f8593f61e2eab3/internals/ot_process_reminders.py) makes a lot of assumptions based on the 4-week cadence off the Chrome release schedule. We'll need to update our logic in a way that handles the new 2-week schedule, with a solution that is able to gracefully handle the 4-week schedule up until M153, when we switch to the 2-week schedule. Ideally, we make changes in a way that can facilitate further schedule changes without major overhauls in the notification logic again.