RFR: 8280026: Cleanup of IGV printing

[Nils Eliasson]

This is a clean up of the code that controls the printing of IGV graphs. This is preparatory work for another patch.

* Default params removed when they are only used in the non-default case.
* Moved code around so that methods with similar concern are kept together
* Move some code from hpp to cpp file
* Changed name of print_method with actual implementation to print_method_impl to clarify intent
* Removed the print_method that was used with a node idx. I once introduced it for debugging - but now there are also other versions that pass a node.

Please revew,
Nils

-------------

Commit messages:
 - IGV printing cleanup cont
 - IGV printing cleanup

Changes: https://git.openjdk.java.net/jdk/pull/7088/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7088&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8280026
  Stats: 91 lines in 3 files changed: 34 ins; 40 del; 17 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7088.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7088/head:pull/7088

PR: https://git.openjdk.java.net/jdk/pull/7088