RFR: JDK-8303575: adjust Xen handling on Linux aarch64

Fri Mar 3 13:03:03 UTC 2023

After [JDK-8301050](https://bugs.openjdk.org/browse/JDK-8301050) the Xen handling on aarch64 should be slightly adjusted.
The output in VM_Version::print_platform_virtualization_info was missed and needs to be added for Xen.
Additionally a new XenPVHVM virtualization type could be introduced because this describes the Xen on aarch64 better.
See also https://community.arm.com/arm-community-blogs/b/architectures-and-processors-blog/posts/virtualization-on-arm-with-xen where the naming is used.

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Commit messages:
 - JDK-8303575

Changes: https://git.openjdk.org/jdk/pull/12853/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12853&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303575
  Stats: 13 lines in 3 files changed: 5 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/12853.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12853/head:pull/12853

PR: https://git.openjdk.org/jdk/pull/12853