[feat] Migrate to GTK4

[darkdragon-001]

Describe the problem

A lot of development has happened in GTK4 - especially in the area of accessibility to run with different controls (e.g. touch screen) and diverse screen sizes (e.g. phones and tablets). It would be great if Tauri would upgrade to GTK4.

Describe the solution you'd like

Upgrade to gtk-rs using GTK4.

Alternatives considered

No response

Additional context

No response

[ildella]

https://gtk-rs.org already supports GTK-4

[paul-hansen]

Note that the gtk3 crate is now archived: https://github.com/gtk-rs/gtk3-rs