As proposed in T95802, this adds buttons to modify the override in the library override display mode. {F12901085} Some further usability improvements are planned. E.g. this does not yet expand collections (modifiers, constraints, etc) nicely or group modified properties of a modifier together. The following shows a overridden modifier property and how added modifiers are listed: {F12901098}
I decided to add the right column so that the left column can be scrolled independently, like we do it for the restriction toggles in other display modes. This differs from the Data API mode, [[ https://developer.blender.org/T95802#1314065 | which has some issues ]] in my opinion.
Contains some cleanups that are to be committed separately, just uploading it all as one patch for some quick review.