output: remove ported wlr_output functions

output: remove ported wlr_output functions

We have several wlr_output_* functions which are just wrappers around
corresponding wlr_output_state_* functions and don't actually touch the
wlr_output itself. These probably made some sense historically, but IMHO
they are just confusing now. So remove them and call wlr_output_state_*
directly.

Rename wlr_output_commit() (still useful) to output_state_commit().