Allow using callee-save registers when WASM SIMD is enabled
<rdar://problem/103929372>
Pull request: https://github.com/WebKit/WebKit/pull/8254
Committed 258757@main (63b6c42ff2b8): <https://commits.webkit.org/258757@main> Reviewed commits have been landed. Closing PR #8254 and removing active labels.