[crac] RFR: 8373781: [CRaC] Permit -XX:CPUFeatures on other platforms

[Radim Vansa]

Currently `-XX:CPUFeatures` option is available only on `x86_64`. This complicates creating multiarch container images that are meant to be universally runnable (with `-XX:CPUFeatures=generic`).

I propose to make this option available on all architectures, with the non-arch specific values:
* `generic`
* `native`
* `ignore`

The implementation on non-x86_64 will only validate the sanity of the value.

The related option `-XX:+ShowCPUFeatures` will print an informative message (saying that the option does not make much sense).

`-XX:+IgnoreCPUFeatures` will be permitted as well, but it will be a no-op on the other architectures.

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Commit messages:
 - 8373781: [CRaC] Permit -XX:CPUFeatures on other platforms

Changes: https://git.openjdk.org/crac/pull/282/files
  Webrev: https://webrevs.openjdk.org/?repo=crac&pr=282&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8373781
  Stats: 85 lines in 19 files changed: 56 ins; 14 del; 15 mod
  Patch: https://git.openjdk.org/crac/pull/282.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/282/head:pull/282

PR: https://git.openjdk.org/crac/pull/282