"Owning" MouseRelease/MouseMove callback behaviour makes things difficult

Currently a receiver processing MousePress and returning true, will lock itself into being the only (or at least, priority) receiver for further mouse events.

What is worse, if a button receiver 'owns' the callbacks, then someone listening for a different button won't get them either.

This needs some kind of solution, and possibly in a backwards compatible way, maybe some new mechanism, so the old one can be preserved, maybe deprecated or maybe not.

Related, or maybe the same issue as https://github.com/beyond-all-reason/spring/issues/910, but that one is worded in a too specific way to focus on the problem itself.

Start by tracing the MousePress, MouseRelease, and MouseMove callback dispatch paths, then compare the problem with related issue 910. Clarify whether ownership should be preserved, deprecated, or replaced, and define done as allowing independent button listeners to receive relevant events without an undefined compatibility break.

Written by the indexing model from the issue text.