Intent to ship: Explicit Resource Management

[Daniel Minor]

As of Firefox 141, I intend to enable Explicit Resource Management by default on all platforms. It is currently available in Nightly builds, disabled by default and controlled by the `javascript.options.experimental.explicit_resource_management` preference. Explicit resource management adds a new `using` keyword and allows for automatic disposal of resources when a variable leaves a scope. Our implementation was contributed by a volunteer, Debadree Chatterjee. This was a large and complicated proposal, thanks for all of the work Debadree :)

The proposal reached Stage 4 of the TC39 process on May 28th. V8 shipped their implementation in Chrome 134: https://developer.chrome.com/release-notes/134#explicit_resource_management_async, and work is underway in JavaScriptCore, the tracking bug is https://bugs.webkit.org/show_bug.cgi?id=248707 (with some features landed e.g. in https://bugs.webkit.org/show_bug.cgi?id=292523).

Bug to turn on by default: https://bugzilla.mozilla.org/show_bug.cgi?id=1967744

Standard: https://github.com/tc39/proposal-explicit-resource-management

[Debadree Chatterjee]

Very happy to see this! Thank you so much! would also like to thank Arai for all the help, reviews and explanations along the way all of them were invaluable and I learnt a lot!