RFR: 8312443: sun.security should use toLowerCase(Locale.ROOT)

[John Jiang]

sun.security codes should use `toLowerCase(Locale.ROOT)` instead of `toLowerCase()`.
In addition, no `toUpperCase()` was found in this code scope.

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Commit messages:
 - 8312443: sun.security should use toLowerCase(Locale.ROOT)

Changes: https://git.openjdk.org/jdk/pull/14948/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14948&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8312443
  Stats: 9 lines in 3 files changed: 2 ins; 1 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/14948.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14948/head:pull/14948

PR: https://git.openjdk.org/jdk/pull/14948