Allow streamed client side navigation to be compressed (gzip/brotli) by proxies

[Smirow]

Describe the problem

Streamed (defered) client side navigation cannot be compressed by proxies because of the proprietary MIME introduced in #9142.

Describe the proposed solution

Next seems to be going for text/x-component for rsc which is a bit strange, and will not resolve the buffering issue tackled by #9142.

X-Content-Type-Options=nosniff should prevent browsers from buffering, but the buffering behavior described here will be extended to client side navigation (though it will make it consistent between client side navigation and full page load 🥲).

Alternatives considered

No response

Importance

would make my life easier

Additional Information

Not sure if it should be a bug report.