Add stream responses

[tryvin]

With Lambda Function URLs supporting RESPONSE_STREAM, we can make the response()->stream() function work as intended, streaming the contents as they are received.

This then adds the new HttpResponse with Generator support from bref/bref support to the Octane handler.

Depends on: https://github.com/brefphp/bref/pull/1980

[tryvin]

@mnapoli PHP stan fixed.