chore(main/vlc, x11/vlc-qt): set default video output to xcb

[twaik]

Fixes #19613 Fixes #20671

It is a patch update improving performance by setting XCB video output as default.

I will merge it in 72 hours if no one minds. Or anyone else can merge it earlier.

[twaik]

TBH I have no idea. I did not dive deep to mpv sources.

[TomJo2000]

Gonna look into it on my own time then.

Edit: It looks like MPV isn't affected by this problem.

[TomJo2000]

resolves #20671 I'd wager this issue is also related.

^{Edit 1: I don't think that properly linked so I'll add it manually on the issue. Edit 2: Oh looks like resolution keywords only apply if used by the author of a PR, that makes sense in hindsight.}