Add WebCore::WebGPU enumerations and additional serialization updates.
<rdar://problem/115904551>
Pull request: https://github.com/WebKit/WebKit/pull/18094
Committed 268336@main (f8aa338b7eb4): <https://commits.webkit.org/268336@main> Reviewed commits have been landed. Closing PR #18094 and removing active labels.