chore: optionally prefix authentication related cookies (#22148)

When the deployment option is enabled auth cookies are prefixed with
`__HOST-`
([info](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Set-Cookie)).

This is all done in a middleware that intercepts all requests and strips
the prefix on incoming request cookies.

enterprise/wsproxy/wsproxy.go

@@ -332,6 +332,7 @@ func New(ctx context.Context, opts *Options) (*Server, error) {
 		sharedhttpmw.Recover(s.Logger),
 		httpmw.WithProfilingLabels,
 		tracing.StatusWriterMiddleware,
+		opts.CookieConfig.Middleware,
 		tracing.Middleware(s.TracerProvider),
 		httpmw.AttachRequestID,
 		httpmw.ExtractRealIP(s.Options.RealIPConfig),