gtk/imwayland: Use serial to control outbound messages
Following the text-input protocol changes at https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/115, use the serial number to have the client push changes to the zwp_text_input_v3 object only after compositor/client states match.
This specifically is more lenient to compositors pushing multiple .done events ahead of the client replying to them.
(cherry-picked from commit f108f053)
Fixes: #4853 (closed)