breadcrumb refinements

[ara4n]

we should use Tooltip rather than HTML tooltips to show the room names, so you don't have to wait ages for the HTML tooltip to appear. Also, we should allow the list to be horizontally scrolled (as the grey gradient on the RHS implies)

[AmandineLP]

Maybe we should also display the space for breadcrumbs only when the first room is here to populate it

[AmandineLP]

Also, for tracking: the room should move up when we view it rather than when we move away

[AmandineLP]

Potential idea for later: add a red/grey dot when new msg came in the room

[lampholder]

also (from #8549) breadcrumbs should persist over refreshes

[turt2live]

I've broken this out for easier tracking and bug squashing:

• Breadcrumbs should use Tooltip, not title attributes #9303
• Breadcrumbs should be scrollable #8714
• Consider always showing the current room in the breadcrumbs #8659
• breadcrumbs need badges #8606
• breadcrumbs should persist over refreshes #8549