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.

docs/reference/api/general.md

@@ -314,6 +314,7 @@ curl -X GET http://coder-server:8080/api/v2/deployment/config \
     "hide_ai_tasks": true,
     "http_address": "string",
     "http_cookies": {
+      "host_prefix": true,
       "same_site": "string",
       "secure_auth_cookie": true
     },