[11u] RFR (XS) 8240751: Shenandoah: fold ShenandoahTracer definition

[Aleksey Shipilev]

Original RFE:
   https://bugs.openjdk.java.net/browse/JDK-8240751
   https://git.openjdk.java.net/jdk/commit/382b8fed

The context have changed, so patch does not apply cleanly. The patch itself is rather trivial.

11u webrev:
   https://cr.openjdk.java.net/~shade/8240751/webrev.11u.01/

Testing: Linux x86_64 {fastdebug,release} builds

-- 
Thanks,
-Aleksey