Requests: Add `inputActive` field to `GetInputList` response

[awfulcooking]

Description

Adds inputActive bool to objects in the GetInputList response

Motivation and Context

There isn't currently a way to determine which inputs are active, without hacks(*)

This field makes loading the state much easier. So we can show only active inputs in an audio mixer, like the OBS frontend does.

(* Only active inputs are sent in the high frequency InputVolumeMeters event, so you can filter based on an input's presence in that)

How Has This Been Tested?

Tested OS(s): compiles in a Linux container ☑️

Can't easily test further atm.

Checklist:

• [x] I have read the Contributing Guidelines.
• [x] All commit messages are properly formatted and commits squashed where appropriate.
• [x] My code is not on master or a release/* branch.
• [ ] The code has been tested.
• [x] I have included updates to all appropriate documentation.