RFR: 8271471: [IR Framework] Rare occurrence of "<!-- safepoint while printing -->" in PrintIdeal/PrintOptoAssembly can let tests fail [v4]

[Christian Hagedorn]

> A test VM used by the IR framework sometimes prints `` in the middle of emitting a `PrintIdeal` or `PrintOptoAssembly` output which could lead to IR matching failures:
> https://github.com/openjdk/jdk/blob/489e5fd12a37a45f4f5ea64b05f85c6f99f70811/src/hotspot/share/utilities/ostream.cpp#L918-L927
> 
> I thought about just bailing out of IR matching if this string is found after a failure but this issue also affects internal framework tests (I observed one case locally where this happened in the test `TestIRMatching`, letting it fail).
> 
> Handling `` makes things more complicated for the IR framework tests. I'm not sure about the value of printing this message in the first place. But if nobody objects, I suggest to either remove it or at least guard it with `Verbose`, for example. I went with the latter solution in this PR.
> 
> Thanks,
> Christian

Christian Hagedorn has updated the pull request incrementally with one additional commit since the last revision:

  Renaming and change handling for TestScenarios

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4932/files
  - new: https://git.openjdk.java.net/jdk/pull/4932/files/ea3b6a6b..8cc6b667

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4932&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4932&range=02-03

  Stats: 53 lines in 4 files changed: 18 ins; 12 del; 23 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4932.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4932/head:pull/4932

PR: https://git.openjdk.java.net/jdk/pull/4932