Persona bar: Show page title on hover, show more of long page titles

[OllyHodgson]

Fixes #3090.

1. No longer truncates the page name. This means screen readers should be able to read the entire page name.
2. Handles the text-overflow using CSS.
3. Adds the page name to the title attribute of the list item. Most desktop browsers will show this when hovering over the page name.
4. Tightens up the spacing a little, so slightly longer page titles fit. I'm pretty sure there's more we can do here, but I think this is a decent start.

I've tested in latest Chrome, Edge (Chromium) and Firefox. Could do with testing in a wider variety of browsers.

Summary

[dnfclas]

All CLA requirements met.

[mitchelsellers]

Lgtm

[david-poindexter]

Looks good - thanks @OllyHodgson

[valadas]

Nice one, thanks!