http: set socket.server unconditionally

This is useful for situations in which the socket was not
created for HTTP, e.g. when using arbitrary `Duplex` streams.

(The added test fails because previously, `socket.server.emit()`
would not work for emitting the `clientError` event, as
`socket.server` was `undefined`.)

PR-URL: https://github.com/nodejs/node/pull/30571


Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>