<i18n dev> RFR: 8318186: ChoiceFormat inconsistency between applyPattern() and setChoices()

[Justin Lu]

Please review this PR which clarifies inconsistency between `ChoiceFormat::applyPattern` and `ChoiceFormat::setChoices`.

A `ChoiceFormat` is composed of limits and formats. `applyPattern()` will throw an exception if limits are not in ascending order, while `setChoices()` will not. This should be clarified in the specification of `applyPattern()`.

-------------

Commit messages:
 - change from impl spec to API spec
 - init

Changes: https://git.openjdk.org/jdk/pull/16317/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16317&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318186
  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/16317.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16317/head:pull/16317

PR: https://git.openjdk.org/jdk/pull/16317