Some bindgroups do not get deduplicated

[sagudev]

Description
Discovered in #6012 (comment), sometimes (compatible) bindgroups with same content are not deduplicated, therefore not detected as equal (I suspect the problem originates from layouts that come from getBindGroupLayout).

Repro steps
Repro is here: https://github.com/sagudev/wgpu-problem/tree/another-empty-bind-panic-2. This is webgpu:api,validation,encoding,programmable,pipeline_bind_group_compat:default_bind_group_layouts_never_match,render_pass:pipelineType="auto0";bindingType="auto0";swap=true;empty=false;renderCommand="draw" but rewritten in rust (and to wgpu).

Expected vs observed behavior
Per CTS there should actually be no error (bind groups are the same in content): https://github.com/gpuweb/cts/blob/198d1770062c1a8aba86e7d6e001bb47bea028ee/src/webgpu/api/validation/encoding/programmable/pipeline_bind_group_compat.spec.ts#L960

When this is done it should be safe to revert 60b42f9 (ping me for CTS run on servo)

[teoxoy]

It turns out that we are not deduplicating derived BGLs at all.

[sagudev]

Why exactly BGL needs to work using deduplication, can't we just operate with duplicated bindgrops and check for compat by content, to me it seems like a big footgun.

[teoxoy]

I'm not sure that the underlying APIs allow that. I tried reducing potential misuse (forgetting to deduplicate) but it didn't work out since the other code-path that creates BGLs is quite different.