Intent to ship: WebAssembly GC

[Ryan Hunt]

As of Firefox 120 I intend to turn WebAssembly GC on by default on all platforms.

Summary: The WebAssembly GC proposal extends wasm with managed low level data types (structs/arrays) which allow managed languages (such as Java/Dart/Kotlin) to use the host garbage collector when compiling to WebAssembly. This makes it possible for reference cycles between the guest language and host browser to be collected. There are also potential size and performance benefits.
Standards Body: WebAssembly Community Group
Specification: https://github.com/webassembly/gc
Explainer: https://github.com/WebAssembly/gc/blob/master/proposals/gc/Overview.md

Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=wasm-gc
Bug to turn on by default: https://bugzilla.mozilla.org/show_bug.cgi?id=1845373
Platform coverage: All platforms
Preference: javascript.options.wasm_gc
DevTools bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1855254
Other browsers:

    Blink: Shipping in version 119 (https://groups.google.com/a/chromium.org/g/blink-dev/c/K_GpDF0y5Q8/m/XIJSfbTHBwAJ)
    WebKit: Has an experimental implementation, no public signals or commitment (https://bugs.webkit.org/show_bug.cgi?id=247394)

web-platform-tests: Covered by shared wasm spec tests (https://github.com/WebAssembly/gc/tree/main/test/core/gc)
TAG Review: https://github.com/w3ctag/design-reviews/issues/814