Make "iris" DRI the default for Gen 8+ GPUs

[PlayNeth]

Describe the feature

The iris mesa driver is needed for the DDX driver to work properly on modern intel GPUs

And if possible, update the documentation to refer to it as well.

It should be done because

Otherwise it falls back to the swrast DRI driver, and performance is much worse.

What are the alternatives?

No response

Additional context

No response

Extra fields

• I have checked the existing issues
• I have read the Contributing Guidelines
• I'd like to work on this issue

[cepelinas9000]

@PlayNeth Are you referring to https://gitlab.freedesktop.org/xorg/driver/xf86-video-intel/-/issues/229 this issue?

[PlayNeth]

Nope. DRI 3 is currently the default for the driver on xlibre, but the problem with gen 8+ igpus is that they don't support it so they fallback to swrast for the AIGLX