The reason for this flake is it missed clicking on the Set
All button (`.subs_set_all_users`) because it calculated
its position before/during it starts scrolling.
There are two scrolling events caused by typing `ot`,
* First is due to internal focus call before typing
which scrolled down the page to bring input in the view.
* Second is after it typed `ot` the user list is updated to
one value, which caused the modal height to decrease rapidly.
Note: It theory, there is three scrolling event,
First is of course internal focus then, after it typed `o`
the list is updated to two values and one is after `t` the
list is updated to a single value.
But as puppeteer is very quick it directly jumped to the
scrolling event after it typed `ot`.
For a more detailed explanation read,
https://chat.zulip.org/#narrow/stream/43-automated-testing/topic/master.20failing/near/1173996.
This commit just temporarily fixes this flake, it's not the
best approach to use time-based delays as they can't be
robust (e.g If the machine is super slow then time-based
delays can fail.).
This commit fixes a rare flake which was most probably
caused when we clicked on the `Check All` button, and
we instantly cleared the filter when it was still marking
the user `checked`, which nullified the effect of clicking
on `Check All` button.
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.
