[WebGPU] de-couple vertex buffer binding indices from bind group binding indices
<rdar://problem/104673394>
Pull request: https://github.com/WebKit/WebKit/pull/9161
Committed 259414@main (1303b0d0d672): <https://commits.webkit.org/259414@main> Reviewed commits have been landed. Closing PR #9161 and removing active labels.