Interpreter for-await ignores an async generator Symbol.asyncIterator override #3632

async function* source() { yield 1; }
const gen: any = source();
gen[Symbol.asyncIterator] = function () {
    let done = false;
    return {
        next() {
            if (done) return { done };
            done = true;
            return { done: false, value: 7 };
        }
    };
};
async function main() { for await (const value of gen) console.log(value); }
main();

Run with --no-tsconfig --noLib. The SharpTS interpreter prints 1. Node (with the type annotation removed) and a saved SharpTS assembly built with --compile --verify print 7.

for await should call the generator object's own Symbol.asyncIterator override. The interpreter's TryGetAsyncIterator takes the built-in async generator fast path before looking up the symbol. Found while working on #3616 and #3618.