Remove a deprecated MESSAGE notification and listeners

• User impact:

  Low
• Affects Docs:

  Yes
• Migration Impact:

  Any mention of MESSAGE notification or MessageNotificationListener must be reviewed for replacement either with ComponentMessageNotification or EndpointMessageNotification together with their listener counterparts.
• Similar Issues:

  None

The classs hierarchy of Message (deprecated), EndpointMessage and ComponentMessage doesn't message the class hierarchy of their listeners, which wreaks havoc on generics and the code isn't compilable.

Given that is it deprecated, remove it from the codebase and make way for generics in notification listeners.