When animators want to key something in the viewport,
the code needs to know *which properties* should be keyed of that selected thing.
So far that was done with keying sets, and a pop-up that let's
you choose the keying set to use. You can get rid of the popup by
choosing a keying set ahead of time. But that is also not always desirable.
That pop-up is quite confusing and gives way too many options.
To simplify this process this PR adds a User Preference option to choose one or more of:
* Location
* Rotation
* Scale
* Rotation Mode
* Custom Properties
Now whenever the `I` key is pressed in the viewport,
and no keying set is enabled, it reads the preferences for which channels to insert.
# User Facing changes
* The popup will not be shown when pressing the hotkey,
but you can still explicitly use keying sets by going to the menu
* Which channels are keyed is defined by a User Preference setting under animation
* when a keying set is used explicitly, the User Preference settings are ignored
Part of #113278
Pull Request: https://projects.blender.org/blender/blender/pulls/113504
a99e419b6e