Reduce headerbar updates

[jeremypw]

While investigating another issue it was noticed that the updating/synchronization of the headerbar was unnecessarily convoluted. Too many things could trigger an update. This PR is an attempt to make it simpler and less redundant.

• Changing the "active" slot only triggers an update if a Miller view is used otherwise the header is only updated when the active tab changes. (Only with a Miller view can the active slot change without a tab change)
• Most of the updates are done while the directory is loading; the browser buttons are updated after.
• Updating the pathbar is done in the same function as the rest of headerbar
• Updating the pathbar in tab restore function discontinued as it has already been done at that point
• Update location bar function absorbed into update headbar and always animate