<i18n dev> RFR: JDK-8319628: DateFormat does not mention IllegalArgumentException for invalid style args

[Justin Lu]

Please review this PR and [CSR](https://bugs.openjdk.org/browse/JDK-8319868) which makes IllegalArgumentExceptions apparent for the _j.text.DateFormat_ static factory methods that have the _style_ parameter.

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Commit messages:
 - init

Changes: https://git.openjdk.org/jdk/pull/16624/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16624&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319628
  Stats: 6 lines in 1 file changed: 2 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/16624.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16624/head:pull/16624

PR: https://git.openjdk.org/jdk/pull/16624