Preferences: Replace SettingsSidebar and SimpleSettingsPage

[ryonakano]

Problem

We're currently using Granite.SettingsSidebar and Granite.SimpleSettingsPage for the preference view:

But these widgets were moved to Switchboard and deprecated in Granite 7 (see elementary/switchboard#265) so we would see the deprecation warning when we port Monitor to GTK 4.

Proposal

Replace SettingsSidebar and SimpleSettingsPage with another widget, maybe Gtk.StackSwitcher?

Prior Art (Optional)

No response

[stsdc]

I agree. This PreferencesView needs also a redesign and visual cleanup.
Also on the top left and bottom right corner we can see how content overflows the Popover container.