<i18n dev> RFR: 8314925: ChoiceFormat does not specify IllegalArgumentExceptions

[Justin Lu]

Please review this PR and [CSR](https://bugs.openjdk.org/browse/JDK-8315148) which is a conformance change to specify exceptions in java.text.ChoiceFormat.

Makes `IllegalArgumentException` apparent for `applyPattern` and `setChoices`, as well as for the associated constructors that call the methods.

This change also improves the error message for the `setChoices` IAE.

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Commit messages:
 - Include constructor + grab exceptions from 'pull/15392'
 - init

Changes: https://git.openjdk.org/jdk/pull/15473/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15473&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8314925
  Stats: 9 lines in 1 file changed: 8 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15473.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15473/head:pull/15473

PR: https://git.openjdk.org/jdk/pull/15473