RFR (XS) 8241926: Shenandoah: only print heap changes for operations that directly affect it

[Aleksey Shipilev]

RFE:
  https://bugs.openjdk.java.net/browse/JDK-8241926

Our current log prints the heap changes for every operation, including those that do not change the
heap directly. It clutters the GC log unnecessarily. We might consider only printing heap changes
for the ops that do affect either used() or capacity().

Example log is in the issue itself.

Webrev:
  https://cr.openjdk.java.net/~shade/8241926/webrev.01/

Testing: hotspot_gc_shenandoah, eyeballing gc logs

-- 
Thanks,
-Aleksey