Migrate the About page in Settings.

This change adds the "About" page and the "Device name" Preference.

However, due to the lack of editable text support in the alert dialog (SPA widget), the device name can't be changed at the moment.

Bug: 269486170
Test: manual, see screenshots.
Change-Id: Ie6b034d82b1718c8f22366ef525fd6d36e4df9ad