In-line reminders in places where future dates are available

There are several places where we can add quick reminder sets, similar to apps like Netflix and Reddit do:

• Activities with future time open dates set: Quiz, assignment and feedback
• Future courses
• Activities with availability time restrictions set
• Sections with availability time restrictions set

This could connect with MOBILE-3908 although it won't necessarily create a calendar reminder (maybe is not necessary? We can just add quick reminders, not events like Google does)

This needs some shaping, some ideas:

• After a reminder is set, the icon changes colour and becomes active (check Netflix and Reddit)
• To cancel or re-schedule a reminder, click on the active icon and options will be displayed in an in-line popup to delete/re-schedule maybe?
• Notifications tab in the app should have an option to see active reminders (so they can be deleted from there as well or you can go to the related activity)