Draft: add support for the P010 format, and pave the way for color representation support

With this, it's possible to play back HDR videos with hardware acceleration and pass it to KWin without additional copies, and if no tone mapping is required, KWin can pass it to the display without copies as well.

With color representation, there can be YUV-type formats that require more than just a matrix to convert to RGB (namely ICtCp), but we can take care of that additional complexity later.

Draft because this targets 6.3; it's not important enough for a feature freeze exception.