general: Port to new libadwaita widgets

Christopher Davis requested to merge wip/cdavis/use-new-adaptive-widgets into main

This MR is a big one, and it's hard to effectively split due to the nature of the changes. This MR ports Settings to the new libadwaita 1.4 widgets, including AdwToolbarView, AdwNavigationView, and toward the end AdwNavigationSplitView and AdwBreakpoint.

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