PredefinedDynamicTraceEventParser should support dynamic events from EventPipeEventSource as well as ETWTraceEventSource.

I believe this can be done in the following way:

• Update OnUnhandledEvent to look at data.Source and handle EventPipeEventSource differently than EtwTraceEventSource.
• EventPipeEventSource should look at data.eventRecord and use that to figure out what event we're dealing, get the template, and register it by calling source.RegisterEventTemplate and OnNewEventDefinition.

Don't change any of the existing implementations of TraceEventParser. We'll do this after we get the implementation of PredefinedDynamicTraceEventParser close enough.