Support shadow mode in local ratelimit rule.

*Description*:
Support shadow mode in local ratelimit rule.
For the Global rate limit case, it is handled in this PR. https://github.com/envoyproxy/gateway/pull/7630

[optional *Relevant Links*:]
original Issue: https://github.com/envoyproxy/gateway/issues/6786
https://github.com/envoyproxy/gateway/pull/7630#discussion_r2575361287
