input: more mp_msg conversion

It appears the last run missed all mp_tmsg().

Since the command parser also prints messages, it needs a new parameter
to pass a log context. We go the easy way and just require the input_ctx
to be passed, and use its mp_log.
input: handle MOUSE_LEAVE specially

Do this so that MOUSE_LEAVE can't be combined with other keys. (E.g.
keep 'w' pressed, then move the mouse outside of the mpv window; it will
print a warning what w-MOUSE_LEAVE is not mapped.)
input: translate mouse position to OSD space early

Until now, mouse positions were just passed to the core as-is, even if
the mouse coordinates didn't map to any useful coordinate space, like
OSD coordinates. Lua scripting (used by the OSC, the only current user
of mouse input) had to translate mouse coordinates manually to OSD space
using mp_get_osd_mouse_pos(). This actually didn't work correctly in
cases mouse coordinates didn't map to OSD (like vo_xv): the mouse
coordinates the OSC got were correct, but input.c was still expecting
"real" mosue coordinates for mouse areas.

Fix this by converting to OSD coordinates before passing the mouse
position to the core.