[crac] RFR: 8364538: [CRaC] Test CRaCIgnoreRestoreIfUnavailable [v4]

[Timofei Pushkin]

> Adds tests for `CRaCIgnoreRestoreIfUnavailable`.
> 
> The case for incompatible CPU features is not tested, although I believe it should work. Such test would be more complex (to the best of my knowledge, emulation is needed to be able to reduce the set of available features between checkpoint and restore) so it deserves a separate task. It would be something like what `test/jdk/jdk/crac/CPUFeatures/CPUFeatures.sh` does (have never run it, not sure if it works).

Timofei Pushkin has updated the pull request incrementally with one additional commit since the last revision:

  Run NoCPUFeaturesTest only on Linux

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Changes:
  - all: https://git.openjdk.org/crac/pull/255/files
  - new: https://git.openjdk.org/crac/pull/255/files/7ef6c30e..e93f742c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=crac&pr=255&range=03
 - incr: https://webrevs.openjdk.org/?repo=crac&pr=255&range=02-03

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/crac/pull/255.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/255/head:pull/255

PR: https://git.openjdk.org/crac/pull/255