xwayland: assume no WM_HINTS means window wants input
xwayland: assume no WM_HINTS means window wants input

Some X11 clients (e.g. Chromium, sxiv) don't set WM_HINTS. The spec
says:

> Window managers are free to assume convenient values for all fields of the
> WM_HINTS property if a window is mapped without one.

Our wlr_xwayland_icccm_input_model function assumes missing WM_HINTS
means the window doesn't want input, but this is incorrect. Assume the
window wants input unless it explicitly opts-out by setting WM_HINTS.

Closes: https://github.com/swaywm/sway/issues/6107

SirCmpwn/wlroots,swaywm/wlroots,swaywm/wlroots