So that Firefox is easier for me to learn, as a user syncing multiple devices, I want to be able to filter and locate my synced tabs in a sidebar just like history and bookmarks instead of a web-based view.

Acceptance criteria:
* A sidebar option as depicted in URL is always available under View > Sidebar
* When filtering/searching the sidebar only matching tabs are displayed
* When unauthenticated, when the user opens the sidebar, they can read a description of the benefit of synced tabs with a link to preferences
* When tab syncing is disabled, when the user opens the sidebar, they are encouraged to re-enable tab syncing on the preferences page
* When syncing single device, information is presented to encourage adding another device with links to clients
* When Firefox Account password has changed, the user is encouraged to sign in