If you have two browsers open for the same account, muting in one
browser will now be reflected in the other browser. This got
regressed when changing the approach from collapsing to hiding.
The new code should be less brittle, as we encapsulate re-rendering
in muting.rerender().
(imported from commit 4e65e265b64513d38f518770453b7436cb92b4ca)
Instead of collapsing muted messages, just hide them altogether
in view where it makes sense to hide them.
(imported from commit 1c2c987ff302ceb135a025753cf421b4de1aea71)
