The title is misleading. These are not part of Firefox. They are in the Test Pilot program, which is a way for Mozilla to gather feedback on what features they should include, how they should change them if they do include them and all in all is completely open-ended. They might also release these as extensions or somesuch. They are all coded as WebExtensions (except for that file-sharing thing, that's just a webpage), so that's very well a possibility.

Also, browsers already have code to record from your microphone, due to the WebRTC web standard, so it's not like this opens an entire new class of potential vulnerabilities.