feat: add lambda-runtime-invocation-id header

[darklight3it]

Summary

Add Lambda-Runtime-Invocation-Id header support for cross-wiring protection.

The RIC now echoes the invocation ID received from RAPID on /next back on /response and /error, enabling RAPID to detect and reject stale responses from timed-out invocations.

Problem

On Lambda Managed Instances (LMI) and On-Demand (OD), when an invoke times out, the runtime process continues running in the background. If a new invoke arrives with the same requestId, RAPID accepts it. The still-running old invocation eventually posts its response, and RAPID matches it to the new invoke — delivering the wrong response (cross-wiring).

Solution

RAPID sends a unique per-invoke nonce via Lambda-Runtime-Invocation-Id header on /next. The runtime echoes it back on /response and /error. RAPID validates the match before accepting the response.

Backward Compatibility

Fully backward compatible in both directions:

• If RAPID doesn't send the header → RIC doesn't see it → doesn't echo → no behavior change
• If RIC doesn't echo it (old version) → RAPID skips validation → no behavior change

Testing

• added unit test
• added a new dockerized test working with the new RIE.