RFR (S) 8240215: Shenandoah: remove ShenandoahAllocationTrace

[Aleksey Shipilev]

RFR:
  https://bugs.openjdk.java.net/browse/JDK-8240215

This was the experimental option to look in the performance of allocation path. It is not needed
anymore, and attempt to turn it on in production would probably introduce performance bottlenecks.
It is safer to remove it, and partially locally revert later if needed.

Webrev:
  https://cr.openjdk.java.net/~shade/8240215/webrev.01/

Testing: hotspot_gc_shenandoah {fastdebug,release}

-- 
Thanks,
-Aleksey