Support setting HDMI/DP content types

[Xyene]

Newer versions of the HDMI and DP specs support specifying a "content type" for the media being presented, one of

• Not defined
• Graphics
• Photo
• Video
• Game

Some monitors will switch display profiles based on these modes. For instance, they may reduce latency in "Game" mode, be more careful with frame timing for "Video", color accuracy in "Graphics", saturation in "Photo", etc.

Wayland allows us to specify the mode of our content through the new content-type-v1 protocol (protocol, discussion, example implementation in mpv). It is up to the compositor to then do something with the mode (e.g., it may only be able to do something if our surface is fullscreen).

For LG's purposes, "Game" is probably the right choice.

If we wanted to be fancy, we could ferry the mode set on the Windows side to the Linux host. I've tried to figure out what Windows calls this through Googles for "DP VSC SDP Content Type", "HDMI InfoFrame", "HDMI Content Type", etc., to no avail, but it must exist because Windows implements this too.

[gnif]

Agreed that "Game" is the right choice here.