fix: Narrow the Dev Server Middleware type

[n0th1ng-else]

Summary

It will be convenient to have the Dev Server Middleware types exported from the rspack. All our middleware is written in separate modules and annotated with JSDoc types.
By exporting the type, we can ge rid of webpack-dev-server mentions in the annotation and use import('@rspack/core').DevServerMiddleware to type the middleware we have.

I have also made an effort to narrow the Middleware type so it is aligned with the one in the webpack-dev-middleware.

(see https://github.com/webpack/webpack-dev-middleware/blob/master/types/index.d.ts#L370)

Example

/**
 * @return {import('@rspack/core').DevServerMiddleware}
 */
module.exports = function DevServerPreflightRequestsMiddleware() {
	return {
		name: 'DevServerPreflightRequestsMiddleware',
		middleware: (req, res, next) => {
			if (req.method === 'OPTIONS') {
				res.statusCode = 204
				res.setHeader('Content-Length', '0')
				res.end()
				return
			}
			next()
		},
	}
}

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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[codspeed-hq]

CodSpeed Performance Report

Merging #10522 will not alter performance

_{Comparing n0th1ng-else:middleware-type (6adc201) with main (8450da9)}

Summary

✅ 12 untouched benchmarks

[chenjiahan]

@LingyuCoder cc~