Allow developers to alter the project list with allow/deny list

Problem/Motivation

Many institutions allow only a vetted subset of modules to be installed on their sites, so it would be nice to allow a developer to alter the list of modules coming in from any particular source.

Proposed resolution

Provide a mechanism whereby a developer can override the list of modules returned from a source. For bonus points, provide a UI to set an allow list/deny list and a radio button where they can choose how the list behaves (as allow vs. deny).

TBD: event / subscriber model? alter hook? plugin/class with a method to override?

Remaining tasks

• ✅ File an issue about this project
• ☐ Manual Testing
• ☐ Code Review
• ☐ Accessibility Review
• ☐ Automated tests needed/written?