RFR (T): 8223018: Rename G1RemSet::*oops_into_collection_set_do methods

[Thomas Schatzl]

Hi all,

  can I have reviews for this change that fixes the
G1RemSet::*oops_into_collection_set_do methods to correspond to the
naming of the main method scan_rem_set again.

CR:
https://bugs.openjdk.java.net/browse/JDK-8223018
Webrev:
http://cr.openjdk.java.net/~tschatzl/8223018/webrev
Testing:
local compilation

Thanks,
  Thomas