fix(deno): echo negotiated WebSocket subprotocol in upgrade response (#4955)

* fix(deno): echo negotiated WebSocket subprotocol in upgrade response

The Deno adapter did not set the `Sec-WebSocket-Protocol` header on the
upgrade response, so browsers such as Chrome rejected connections that
requested a subprotocol. Read the first value from the request's
`Sec-WebSocket-Protocol` header and pass it as the `protocol` option to
`Deno.upgradeWebSocket`, while still honoring an explicitly provided
`protocol` option.

Closes #4439

* add a test

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Co-authored-by: ATOM00blue <219721791+ATOM00blue@users.noreply.github.com>
Co-authored-by: Yusuke Wada <yusuke@kamawada.com>