Improvements to collapsing events

[SpiritCroc]

Desktop is better in collapsing non-message events like membership changes and hidden events. It would be nice if Android would do the following:

• Collapse across multiple dates. Currently, Android doesn't even collapse all events within a date. Could have to do with chunks and pagination.
• Collapse hidden events.

Implementation starting point could be looking at https://github.com/vector-im/element-android/pull/6501/files