Implement pre-flight requests in a standard way

We should handle all requests that are sent as "vanilla" requests (e.g. not modified from the template, no attack strings, etc.) in the same way. I think this should be a standalone part of a Syntribos test that can be disabled if required, but that is used by default to conduct these checks. It should be able to handle connection errors, rate limiting, etc. (common issues that are not specific to any particular test)