Validate copybuffertobuffer() + some spec update

[kunalmohan]

The spec update includes renaming bindings to entries, adding CommandEncoderState and renaming GPUBufferSize to GPUSize64.

r?@jdm @kvark

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• ./mach build -d does not report any errors
• ./mach test-tidy does not report any errors
• These changes fix #___ (GitHub issue number if applicable)

• There are tests for these changes OR
• These changes do not require tests because ___

[highfive]

Heads up! This PR modifies the following files:

• @asajeffrey: components/script/dom/gpubindgrouplayout.rs, components/script/dom/webidls/GPUComputePassEncoder.webidl, components/script/dom/webidls/GPUBindGroupLayout.webidl, components/script/dom/gpucomputepassencoder.rs, components/script/dom/gpubuffer.rs and 6 more
• @KiChjang: components/script/dom/gpubindgrouplayout.rs, components/script/dom/webidls/GPUComputePassEncoder.webidl, components/script/dom/webidls/GPUBindGroupLayout.webidl, components/script/dom/gpucomputepassencoder.rs, components/script/dom/gpubuffer.rs and 6 more

[highfive]

Warning

• These commits modify script code, but no tests are modified. Please consider adding a test!

[kvark]

Thanks!
Don't forget to click "Resolve conversation" for items you address. This helps us see what is WIP and what not.

[jdm]

@bors-servo r=kvark,jdm

[bors-servo]

📌 Commit 1aeae47 has been approved by kvark,jdm

[bors-servo]

⌛ Testing commit 1aeae47 with merge 1a74382...

[bors-servo]

☀️ Test successful - status-taskcluster
Approved by: kvark,jdm
Pushing 1a74382 to master...