Port Project header from HAML to VueJS

Proposal

Following on from porting the right side of the project header to VueJS, the avatar/title/visibility/etc. should also be ported to VueJS (to then be combined with the other Vue apps on the page).

There are 2 approaches to this

Port the whole thing at once

The top left part isn't overly complicated, so everything could be ported at once. This does increase the blast radius of the change, but this can be mitigated with test coverage, and possibly the use of a feature flag.

Port a component at a time

Similar to how the left side was ported to Vue, one component at a time could be ported and merged into the final VueJS app towards the end.

This has the advantage that the blast radius would be limited to the component that is currently being ported without impacting the rest of the header.