[WGSL] Generate the correct code for arrayLength

[tadeuzagallo]

8f80944

[WGSL] Generate the correct code for arrayLength
https://bugs.webkit.org/show_bug.cgi?id=262703
rdar://116524838

Reviewed by Mike Wyrzykowski.

As of 268884@main, the API now exposes the size of runtime-sized arrays at the
end of the argument buffer. This patch updates the compiler to match this argument
buffer layout and rewrite calls to arrayLength to read these sizes.

* Source/WebGPU/WGSL/GlobalVariableRewriter.cpp:
(WGSL::RewriteGlobalVariables::getPacking):
(WGSL::RewriteGlobalVariables::collectGlobals):
(WGSL::RewriteGlobalVariables::containsRuntimeArray):
(WGSL::RewriteGlobalVariables::packArrayType):
* Source/WebGPU/WGSL/Metal/MetalFunctionWriter.cpp:
(WGSL::Metal::emitArrayLength):
(WGSL::Metal::FunctionDefinitionWriter::visit):
* Source/WebGPU/WGSL/tests/valid/array-length.wgsl: Added.

Canonical link: https://commits.webkit.org/268995@main

4091e28

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	🧪 wpe-wk2
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🛠 gtk
	✅ 🧪 ios-wk2-wpt		✅ 🧪 gtk-wk2
	✅ 🧪 api-ios	✅ 🧪 mac-wk2	✅ 🧪 api-gtk
	✅ 🛠 tv	🧪 mac-AS-debug-wk2
	✅ 🛠 tv-sim
✅ 🛠 🧪 merge	✅ 🛠 watch
	✅ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on previous version of this PR (hash 2757bc5)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	❌ 🛠 ios	❌ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
	❌ 🛠 ios-sim	❌ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2
✅ 🧪 webkitperl	❌ 🧪 ios-wk2	❌ 🧪 api-mac	✅ 🛠 gtk
	❌ 🧪 ios-wk2-wpt	❌ 🧪 mac-wk1	✅ 🧪 gtk-wk2
	❌ 🧪 api-ios	❌ 🧪 mac-wk2	✅ 🧪 api-gtk
	❌ 🛠 tv	❌ 🧪 mac-AS-debug-wk2
	❌ 🛠 tv-sim	❌ 🧪 mac-wk2-stress
	❌ 🛠 watch
	❌ 🛠 watch-sim

found an issue

[mwyrzykowski]

Approval is based on having the compiler error fixed, but I tried the change and it works great

[webkit-early-warning-system]

EWS run on current version of this PR (hash 4091e28)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	🧪 wpe-wk2
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🛠 gtk
	✅ 🧪 ios-wk2-wpt		✅ 🧪 gtk-wk2
	✅ 🧪 api-ios	✅ 🧪 mac-wk2	✅ 🧪 api-gtk
	✅ 🛠 tv	🧪 mac-AS-debug-wk2
	✅ 🛠 tv-sim
✅ 🛠 🧪 merge	✅ 🛠 watch
	✅ 🛠 watch-sim

[webkit-commit-queue]

Committed 268995@main (8f80944): https://commits.webkit.org/268995@main

Reviewed commits have been landed. Closing PR #18697 and removing active labels.