Fix IgnoreError

✅ Solution

The "IgnoreError" error in Envoy's ext_proc filter typically arises when the `ProcessorClientImpl::start()` method fails to initialize the gRPC client due to issues like incorrect configuration or connection problems, and the failure is not properly handled, leading to a silent fail-open even if `failure_mode_allow` is false. To fix this, ensure that `ProcessorClientImpl::start()` correctly triggers the configured `onGrpcError` callback when client initialization fails, preventing silent fail-open. Update the code to explicitly check for errors during client creation and propagate those errors to the Envoy connection flow, respecting the `failure_mode_allow` setting.