Optimize CI/CD: Optimize if-nodejs-pr-testing.yml to reduce CI time

## Problem

The centrally managed `if-nodejs-pr-testing.yml` workflow is missing several standard optimizations that would significantly reduce CI time across all AsyncAPI repositories.

### Proposed Changes

1. Add Concurrency Control

2. Add Path Filtering

3. Skip Merge Commits

4. Enable NPM Caching

I’m happy to submit a PR implementing this.
