RFR: 8351851: Update PmemTest to run on AMD64 [v3]

[Ivan Šipka]

> Remove default OS platform linux x86_64, remove @ignores allowing amd64 as a viable OS platform selection

Ivan Šipka has updated the pull request incrementally with one additional commit since the last revision:

  retruning ignore directive to other_arch test case

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Changes:
  - all: https://git.openjdk.org/jdk/pull/24416/files
  - new: https://git.openjdk.org/jdk/pull/24416/files/eae29977..59209dd4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24416&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24416&range=01-02

  Stats: 6 lines in 1 file changed: 5 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24416.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24416/head:pull/24416

PR: https://git.openjdk.org/jdk/pull/24416