Allow optionally suppressing or collapsing membership events in the timeline

**Is your feature request related to a problem? Please describe.**

High activity, especially IRC bridged rooms are hard to navigate due to the join/leave/profile modification messages and disrupts the continuity of a conversation and increases the amount of scrolls needed to find the context/previous message/mention.

**Describe the solution you'd like**

Allow optionally (a toggle) suppressing or collapsing consecutive membership events in the timeline similar to Element Web/Android (for example).