Add feature: requesting WebGPU unknown limits

[captainbrosset]

Specification

Unknown.

Description

Request unknown limits with undefined value.

Documentation

This was added with BCD 5.7.5 via mdn/browser-compat-data#26227.
See https://developer.chrome.com/blog/new-in-webgpu-133#allow_unknown_limits_to_be_requested_with_undefined_value

Browser support

Chrome/Edge 133.

[captainbrosset]

We'll have to decide whether this needs to go into the existing webgpu feature, or be its own separate feature.