Support top-level await in SystemJS modules #32793

Top-level await

console.log('sync');
await new Promise(resolve => setTimeout(resolve));
console.log('async');

->

System.register([], function (exports, context) {
  return {
    setters: [],
    execute: async function () {
      console.log('sync');
      await new Promise(resolve => setTimeout(resolve));
      console.log('async');
    }
  };
});

Where in dependency graphs, SystemJS supports variant B of the top-level await proposal.

Originally posted by Guy Bedford (@guybedford) in #26606