Changes to Analytics Frontend for Managing Stream Response:

- Added `KpiValue` message type in `AnalyticsFrontend.proto`.
- Changed `StartAnalyzer` response type from message to stream.
- Added `StartResponseListener()` call and response handler in the `StartAnalyzer` method.
- Implemented `ConvertValueToKpiValueType` to handle `OneOf` type conversion.
- Added tests to handle stream responses.