wayland-surface: Prefix xdg-shell methods with "xdg_shell_"
wayland-surface: Don't require we manually bump the version for xdg-shell

It's in the protocol as an enum.
Revert "Move window pings to MetaWindow"

This was a bad idea, as ping/pong has moved to a client-specific
request/event pair, rather than a surface-specific one. Revert
the changes we made here and correct the code to make up for it.

This reverts commit aa3643cdde4277a26e5730a0f6335c76a1a22d4f.
Update to new xdg-shell pinging standards