RFR (S): 8145672: Remove dependency of G1FromCardCache to HeapRegionRemSet

[Thomas Schatzl]

Hi all,

  can I have review for the following change that removes the remaining
dependency of G1FromCardCache to HeapRegionRemSet?

G1FromCardCache references some static method that returns some
configuration value for G1FromCardCache. Imo it is better to move that
into G1RemSet as it is some value that is used for configuring parts of
the entire remembered set.

I.e. G1FromCardCache is actually pretty independent of HeapRegionRemSet.

I also removed some unnecessary references to (former)
HeapRegionRemSet::num_par_rem_sets() across the code.

This allows easier hg rm heapRegionRemset* later, or at least adds some
explanation for the methods :)

CR:
https://bugs.openjdk.java.net/browse/JDK-8145672
Webrev:
http://cr.openjdk.java.net/~tschatzl/8145672/webrev
Testing:
jprt

Thanks,
  Thomas