netty: Include pseudo-headers in GrpcHttp2RequestHeaders.iterator() (v1.80.x backport) - #13125

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, gradle/actions/wrapper-validation@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/