Split header

[jeremypw]

Fixes #2456

Splits header with sidebar header just containing the close button
Moving or adding other tools to the sidebar header is left for further PRs as required.

[alainm23]

The design change feels much better, just one question. There is a reason why the navigation buttons (back and forward) are aligned to the center and not to the right?

[danirabbit]

I think the navigation buttons should stay in the right side pane with the view since that's the thing that they take action on. All of our prior art has these buttons in the right side pane as well.

The reason the back button is in the sidebar in System Settings is because it does take action on the entire view including the sidebar there. But here, going back or forward doesn't change the sidebar it just changes the view

[jeremypw]

@danirabbit OK. Is there any other widget that can be moved into the sidebar header to save space on the rh pane? For comparison, Gnome Files has the AppMenu there.

[danirabbit]

GNOME Files has 3 menus, 2 of which are in the right side pane

A menu in the sidebar for some app-wide functions

A menu on the pathbar for actions specific to that folder/path:

A menu for view options

So we already have 2 fewer menus than GNOME Files and 1 fewer menus in the right side pane 😅

[jeremypw]

@danirabbit So nothing in the sidebar header except the close button? If that is the case I am inclined to withdraw this PR as it achieves little and squashes up the widgets in the rh toolbar.

[jeremypw]

Appearance after reversion:

[jeremypw]

@teamcons If we are going to enforce the mantra that the sidebar header can only contain things that act on the sidebar then a search button there would be expected to search amongst the bookmarks, not the view. A search button that acts on the view should be in the view header.