RFR: 8280026: Cleanup of IGV printing [v2]

[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

Nils Eliasson has updated the pull request incrementally with one additional commit since the last revision:

  Feedback

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7088/files
  - new: https://git.openjdk.java.net/jdk/pull/7088/files/d606bd96..ef1f7c72

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7088&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7088&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 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