Implement "Records and Tuples" transform

[rickbutton]

Q	A
Fixed Issues?
Patch: Bug Fix?
Major: Breaking Change?
Minor: New Feature?	👍
Tests Added + Pass?	👍
Documentation PR Link
Any Dependency Changes?
License	Apache-2.0

This PR adds a transform for the Stage 2 Record and Tuple syntax. By default, the transform will look for Record and Tuple in the global, but will optionally look up the names in a module, if either the importPolyfill option is set to true, or a polyfill module name is specified via polyfillModuleName.

We have an experimental polyfill available at https://github.com/bloomberg/record-tuple-polyfill, which I intend to publish as the @bloomberg/record-tuple-polyfill package soon.

We originally open sourced this work under the Apache-2.0 license, and have included said license in the plugin's subdirectory.

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/41210/

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[nicolo-ribaudo]

Thanks Rick! I planned to port the plugin to this repo but never actually found the time to do so. I really appreciate you doing this!

Two things for the Babel team:

1. I have no idea about how licenses work and what it compatible with what. We already have other exceptions in our codebase (you can check them in .gitignore), but they are all MIT.

2. Currently this plugin transforms records and tuples syntax to a call to the builtin, and loads the polyfill for such builtin function.
   This makes this plugin "self-contained", however we might prefer to do something similar to regenerator-runtime (or to other transforms relying on builtins): just inject a reference to the global, and then let our users load the polyfill themselves*. This would make the plugin polyfill-agnostic (however, only one polyfill currently exists), but it requires user to explicitly specify the polyfill.

   In this case, the plugin could be simplified to something like this:

   export default declare(({ template, types: t }) => {
       api.assertVersion(7);
   
       return {
           name: "@babel/plugin-proposal-record-and-tuple",
           inherits: syntaxRecordAndTuple,
           RecordExpression(path) {
               path.node.type = "ObjectExpression";
               path.replaceWith(template.expression.ast`Record(${path.node})`);
           },
           TupleExpression(path) {
               path.replaceWith(
                   t.callExpression(t.identifier("Tuple"), path.node.elements)
               );
           }
       };
   });

* "Themselves" could be using a new polyfill provider in https://github.com/babel/babel-polyfills, or just core-js/es-shims when they implement Record/Tuple support.

[tjpalmer]

I'd love to include this in a YouTube video I want to make this weekend. (Channel with 10K subscribers.) Would be good timing with C# 9 and its records just out. Oh well.

[nicolo-ribaudo]

One minor comment, but otherwise this looks good.

[rickbutton]

apologies for the delay, addressed the comment and resolved the merge conflicts, should be good to go!

[nicolo-ribaudo]

Thanks! And don't worry for the delay, we haven't scheduled 7.13 yet anyway.

[rickbutton]

thanks for the review @JLHwung , I think I've addressed your comments.

[JLHwung]

@rickbutton Thanks! Can you re-run yarn and commit the modified lockfile?

[rickbutton]

@JLHwung done