Modules: improved reporting of unhandled promise rejections.

Modules: improved reporting of unhandled promise rejections.

Previously, some promise rejections were not reported.

For example:

async function timeout(ms) {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            reject(new Error('timeout'));
        }, ms);
    });
}

async function handler(r) {
    let v = await timeout(1000);
    r.return(200);
}