Improve usability of activity list

[mgallien]

People often struggle with activity list when the list is quite long.
Example of issues:

• scrolling in the list to locate something specific can be hard when the list is long
• finding a warning is not always easy unless the top of the list is visible
• finding a Talk or other kind of notifications is not always quick or easy

Should we really keep many entries ?
Currently when the client is propagating changes, they will each get an entry such that the list would display the changes in case the activity server app is not enabled.

[mgallien]

@nextcloud/designers
I will work on providing screenshot as examples of problems.

[PhilippSchlesinger]

There are some existing issues that are related to the activity list:

• [Bug]: Scroll bar shows, but not clickable #5536

• Issue Activities design review #5933 a bunch of improvements (Bugfix/activity list fixes #6064), but I cannot spot the "scroll automatically to top" feature made it into a client release.

• In a comment to a performance related issue Improve speed for initial sync with virtual files #4424 (comment) I proposed to summarize or lazyload activity listing to improve performance.

• [Bug]: Thumbnails not showing under desktop client in VFS mode #6118

• related, but not directly a feature of the activity list: make new and improved share/activities dialogue available within unified search #5458