RFR: 8366864: Sort os/linux includes

[Francesco Andreuzzi]

This PR sorts the includes in hotspot/cpu/linux using `SortIncludes.java`. I'm also adding the directory to `TestIncludesAreSorted.java`.

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Commit messages:
 - add dir
 - sort

Changes: https://git.openjdk.org/jdk/pull/27088/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27088&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8366864
  Stats: 115 lines in 14 files changed: 52 ins; 50 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/27088.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27088/head:pull/27088

PR: https://git.openjdk.org/jdk/pull/27088