val: Test that two 'auto' BGLs at different group indices on the same pipeline are compatible

[kainino0x]

In that case we need to test that 2 bind groups that appear the same, are the same? In other words

      @group(0) @binding(0) var s1: sampler;
      @group(0) @binding(1) var t1: texture_2d<f32>;

      @group(1) @binding(0) var s2: sampler;
      @group(1) @binding(1) var t2: texture_2d<f32>;

If we use layout: 'auto' on this then a bindGroup made with pipeline.getBindGroupLayout(0) should work bound to bind group 1.

I don't think there is a test for that and it would be easy for browsers to disagree on this without a test?

Originally posted by @greggman in #3374 (comment)

[greggman]

#3382