RFR: 8280076: Unify IGV and IR printing

[Nils Eliasson]

This patch adds support for controlling printing of the textual ideal representation (PrintIdeal) in the same way as the printing of IGV graphs currently works. The new flag PrintIdealLevel uses the same phases and levels as the PrintIdealGraphLevel flag. This new flag also gets added to CompileCommand and CompilerDirectives. 

The motivation for this change is to add support for testing during different phases with the TestIR framework.

The old flag (PrintIdeal) is kept intact for now.

This patch is based upon https://github.com/openjdk/jdk/pull/7088

Please review,
Nils

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Depends on: https://git.openjdk.java.net/jdk/pull/7088

Commit messages:
 - Unify IGV and IR printing

Changes: https://git.openjdk.java.net/jdk/pull/7108/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7108&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8280076
  Stats: 71 lines in 7 files changed: 32 ins; 15 del; 24 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7108.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7108/head:pull/7108

PR: https://git.openjdk.java.net/jdk/pull/7108