Intent to ship: WebAssembly js-string-builtins

[Ryan Hunt]

As of Firefox 134 I intend to turn WebAssembly js-string-builtins on by default.

Summary: Provides direct access to JS String builtin functions to WebAssembly.
Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=wasm-js-sb
Bug to turn on by default: https://bugzilla.mozilla.org/show_bug.cgi?id=1913964
Specification: https://github.com/WebAssembly/js-string-builtins/blob/main/proposals/js-string-builtins/Overview.md
Standards Body: WebAssembly CG at the W3C
Platform coverage: All platforms
Preference: javascript.options.wasm_js_string_builtins
DevTools bug: N/A
Other browsers:
    Blink: Shipped since 130 (https://chromestatus.com/feature/6695587390423040)
    WebKit: No status
web-platform-tests: wasm/jsapi/js-string/*