Make the timeout of the rate limit request configurable

[roivaz]

The current timeout value is 5s and not configurable (see code). Also, 5 seconds seems way too high. A more sensible default could be 20ms, same as the envoy ratelimit filter uses.

[alexsnaps]

To be considered whether we'd want 2 of these, or say one "per service", as I could see Authorino needing a different value than Limitador

[adam-cattermole]

I'd say that we include it as part of the extension configuration in the wasm-shim so that it's configurable by service, the same way as the failure mode.