[web] Render AppSwitcher or SettingsSwitcher depending on the navigation

Summary:
When we're in settings route, we need to display SettingsSwitcher. In all the other cases, we should do what we were doing up to this point: render the AppSwitcher.
Depends on D3343

Test Plan: Open chat and check if AppSwitcher is rendered. Change path to settings/account and check if SettingsSwitcher is displayed instead.

Reviewers: benschac, atul, def-au1t

Reviewed By: benschac, atul

Subscribers: ashoat, Adrian, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D3344