Add wgslLanguageFeatures test

[sagudev]

test that returned object is same object (is this done as part of idl tests?)

[kainino0x]

It could go anywhere honestly, either under IDL tests or wherever the other SameObject tests (for adapter.info, etc.) are.

There are no autogenerated IDL tests or anything, so if there isn't a manually written test, none exists.

[greggman]

added. #4175

Ok to close?

[sagudev]

added. #4175

Ok to close?

Yes, I just tested.

BTW there is webgpu:api,operation,device,lost:same_object:* and webgpu:api,operation,adapter,info:same_object:*, but only last one is also done in webgpu:idl,javascript:sameObject:*, so we got missing test and duplication.