Requirements

Add tracking support for the multi-provider to ensure it can emit tracking events for flag evaluations according to the OpenFeature specification (https://openfeature.dev/docs/reference/concepts/tracking/). This should handle event propagation from all child providers, aggregate tracking information, and maintain compatibility with the SDK's tracking APIs and interfaces. The implementation must include tests to confirm that tracking events are emitted correctly from multi-provider scenarios and respect the blocking issue #545. Documentation should be updated to detail how tracking works in a multi-provider context, including any configuration or usage notes for consumers.