Consolidate CloudEvent transformer configuration

- Simplify the CloudEvent transformer by consolidating configuration
  directly into ToCloudEventTransformer class rather than using
  separate configuration objects
- Remove CloudEventProperties and ToCloudEventTransformerExtensions
  classes to reduce abstraction layers and improve maintainability
- Make MessageBinaryMessageReader package-private and convert
  CloudEventMessageConverter methods to static where possible
- Move extension filtering logic into a private inner class within
  the transformer
- Remove CloudEventsHeaders class and CE_PREFIX constant as the
  prefix is no longer used as a configurable value

Author: cppwfs