Have more granular control for each activity in a course

[marcusboon]

Is this a new feature or enhancement? (required)
Feature (but an enhancement to #117)

Is this related to a third-party module in Moodle? (required)
No

Which moodle versions this feature/enhancement can be implemented? (required)
3.5+

Is your feature request related to a problem? Please describe. (required)
Our use case is large courses with a lot of activities (e.g. 50+) of different types.

Describe the solution you'd like (required)

1. Move the configuration of the reminders from the course level to the individual activity; by utilising a coursemodule_standard_elements callback to inject the new settings into the Availability section (or an entirely new section if that makes more sense)
2. Enable a custom schedule per activity e.g. assignment 1 has a due date reminder of 6 days, assignment 2 has a due date reminder of 3 days, quiz 1 has a close date reminder of 4 days etc