[jdk21u] RFR: 8315942: Sort platform enums and definitions after JDK-8304913 follow-ups

[Aleksey Shipilev]

Clean backport to make sure 21u stays in the same shape as mainline.

Additional testing:
 - [x] macos-aarch64-server-fastdebug, `jdk/internal/util/ArchTest.java`

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Commit messages:
 - Backport 1941290b7954033d76527f802bc4c343e8d9f2a8

Changes: https://git.openjdk.org/jdk21u/pull/197/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=197&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315942
  Stats: 29 lines in 3 files changed: 12 ins; 11 del; 6 mod
  Patch: https://git.openjdk.org/jdk21u/pull/197.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/197/head:pull/197

PR: https://git.openjdk.org/jdk21u/pull/197