Fix: Exit http server on php exit

[kozer]

Motivation for the change, related issues

Calling the php.exit caused a hanging connection. This had affect in tests, and leaving open connections around.

Implementation details

Attach the HTTP server that we spawn to handle websocket connections to the PHP instance.
When we call .exit we use the attached instance to close the connections.

Testing Instructions (or ideally a Blueprint)

1. Create a project with the following test code:

import { PHP, __private__dont__use, loadPHPRuntime } from '@php-wasm/universal';

const isWindows = process.platform === 'win32';

const dostuff = async function() {
	const id =  await loadPHPRuntime(
		await getPHPLoaderModule('8.3'),
		await withNetworking({})
	);
	const php = new PHP(id);

	const privateSymbol = Object.getOwnPropertySymbols(php)
		.find(sym => String(sym).includes('__private__dont__use'));


	const result = await php.run({ code: `<?php echo "HI!"; `} );
	console.log(result.text);
	php.exit();

}

dostuff().catch(console.error);

2. Build php-wasm/node and php-wasm/universal

npx nx run php-wasm-universal:build
npx nx run php-wasm-node:build

4. Cd into /dist php-wasm folder and run npm link
5. Go to the project and run npm link @php-wasm/node and npm link @php-wam/universal
6. Navigate inside node module, in each package and run npm install
7. Run the script you have created
8. Ensure that exits successfully

[jeroenpf]

I was able to make this work but we need to add the close() call as well.

I'll take care of this and add a test case tomorrow as well.

[adamziel]

Looking good, thank you so much! For posterity, once we have more of these cleanup callbacks, we may want to introduce something like PHPRuntime.beforeExit: Array<() => void>. For now, though, we're good.