Support the Wayland fractional scale protocol

[LawnGnome]

It would be nice if wezterm supported the Wayland fractional-scale-v1 protocol so that those of us using displays best configured with non-integer scaling factors can get pixel-perfect font rendering.

This protocol is now supported by all the major Wayland compositors in their current stable versions.

[juvevood]

Hyprland has been unable to use wezterm with wayland mode for a long time.

[valpackett]

@juvevood that has nothing to do with fractional scale; that's probably #5103 - #5264