This improves the UX of creating a stream for atleast 1000+ users
realm by showing the the stream creation form much faster than
before.
Search, user addition, scrolling worked smoothly on 15k+
users realm as tested on dev setup.
Also, simplebar is used to replace the default scrollbar.
Fixes#16805
The only downside of this is that it makes it harder to control the
order of these tests; which isn't that important. And the structure
of naming each with its test order fundamentally requires renaming
files when adding/deleting tests, so if we want to control the default
test order, we'd be better off doing that by just hardcoding a list in
the test runner code.
Aman Agrawal
Riken Shah