RFR: 8236263: Remove experimental streaming events

[Erik Gahlin]

Hi,

Could I have review of a fix that will remove experimental events 
related to Event Streaming.

Bug:
https://bugs.openjdk.java.net/browse/JDK-8236263

Webrev:
http://cr.openjdk.java.net/~egahlin/8236263/

Testing:
jdk/jdk/jfr + tier1, tier2

The events have no value for end-users and were added during development 
to find bottlenecks in the implementation. The jdk.Flush event which 
measures total time of a flush will be kept for now, but disabled in 
both default.jfc and profile.jfc. It may be worth mentioning that the 
Event Streaming API can react to data being flushed without a jdk.Flush 
event.

It is possible to do further cleanup. For example, not measure the time 
it takes to flush stack trace data. But since it is late in the release 
and the overhead negligible, I prefer to do that in main line.

Thanks
Erik