enhancement request: Show sidebar searches by default.

[showell]

Particularly for large realms with lots of streams or users, I think we should have the search widgets open by default when you open the app. They're actually quite useful when you learn to use them, but almost nobody's gonna discover them organically. Obviously it takes some real estate to show them, but I think as soon as your realm is big enough that sidebar real estate is an issue, that's exactly when you might want search.

[showell]

Here is what the right sidebar search widget looks like, in case you're wondering what I'm talking about. (And the left sidebar widget is similar.)

[zulipbot]

Hello @zulip/server-sidebars members, this issue was labeled with the "area: right-sidebar" label, so you may want to check it out!