Data modules: Reject the promise on XHR error

[adamziel]

Makes the WordPress data module reject the loading promise on XHR error. Before this commit, the promise would erroneously resolve even if the request failed.

Related to #564

Testing Instructions

Rebuild the WordPress data module as follows:

node packages/playground/wordpress/build/build.js --wp-version=latest --output-js=packages/playground/wordpress/src/wordpress --output-assets=packages/playground/wordpress/public

Then make the following update to the wp-6.4.js file:

// import dependencyFilename from './wp-6.4.data?url';
const dependencyFilename = 'http://localhost:3000/assets/wp-6.4-1d0e58cc.data';
export { dependencyFilename };

Then create a new file called server.js with the following contents:

// Serve static assets from dist/packages/playground/wasm-wordpress-net/, but
// break the connection when the file is 90% downloaded

const express = require('express');
const app = express();
const path = require('path');
const fs = require('fs');

const port = 3000;

app.get('/*', (req, res) => {
	const filePath = path.join(
		__dirname,
		'dist/packages/playground/wasm-wordpress-net/' + (req.query.path || 'index.html')
	);
	const stat = fs.statSync(filePath);
	const fileSize = stat.size;

	const head = {
		'Content-Length': fileSize,
        'Content-Type': 'application/wasm',
        'Access-Control-Allow-Origin': '*',
	};
	res.writeHead(200, head);
	let sentSoFar = 0;
	const stream = fs.createReadStream(filePath);
	stream.on('data', (chunk) => {
		if (sentSoFar + chunk.length > fileSize * 0.9) {
			stream.destroy();
			res.end();
			return;
		}
        res.write(chunk);
		sentSoFar += chunk.length;
	});
});

app.listen(port, () => console.log(`Example app listening on port ${port}!`));

Then run node server.js and npm run dev and go to http://localhost:5400/website-server/

You'll land in a version of Playground where only the first ~90% of the WordPress data module is downloaded and then the connection is cut. You should see the "oops, WordPress Playground had a hiccup" error message.