Calling settings_data.user_can_access_all_other_users on every call to
this function could be expensive when using this function in loops
over every user in the organization.
After the previous commit, those calls are still somewhat expensive
for guest users.
This was added in b387ca4, before we had
`buddy_list.update_empty_list_placeholders`
Now it's not only duplicating that functionality, but will soon
maybe run at the wrong time once the buddy list `populate` starts
making `void` calls to `async` empty list placeholder code.
Opening settings and stream settings UI was not working for guests
if they could not access all users. This was because is_person_active
did not handle inaccessible users correctly, if they were not added in
the users data, when being called in get_group_members to render
group pills.
Instead of showing the "None" empty message, just hide the whole section
instead. Notably this uses the total user counts and not the number of users
rendered, so it's possible we'll still show the sections when they're partially
loaded or if they have inactive users (in which case we'd show the "view more"
links).
The exception is the "THIS CHANNEL" section which we always want to show,
since it can be confusing to see other sections without this section
present. More conversation on that here:
https://chat.zulip.org/#narrow/channel/101-design/topic/right.20sidebar.20design.20tweaks/near/2099241
