[WebGPU] Generated dynamic offsets are incorrect in generated metal source

[Mike Wyrzykowski]

Open https://playcanvas.github.io/#/misc/spineboy

Observe the generated metal source:

    const constant __type0_Packed& global1 = (*(const constant __type0_Packed*)(((constant uint8_t*)&(__ArgumentBuffer_0.global1)) + __DynamicOffsets[0u]));
    const constant __type1_Packed& global5 = (*(const constant __type1_Packed*)(((constant uint8_t*)&(__ArgumentBuffer_1.global5)) + __DynamicOffsets[0u]));

both argument buffers are using the same offset (0), which is wrong, the first should be offset 0 and the second should be offset 1

[Radar WebKit Bug Importer]

<rdar://problem/126365605>

[EWS]

Committed 277439@main (02e0f7667792): <https://commits.webkit.org/277439@main>

Reviewed commits have been landed. Closing PR #27202 and removing active labels.