<i18n dev> RFR: 6228794: [Fmt-Ch] Doc: java.text.ChoiceFormat behavior is not well documented.

[Justin Lu]

Please review this PR and associated [CSR](https://bugs.openjdk.org/browse/JDK-8314546) which expands on the `java.text.ChoiceFormat` specification regarding its pattern.

`j.text.ChoiceFormat` provides an example pattern in the class description, but beyond that it does not specify any well-defined syntax for creating a pattern. In addition, methods related to the pattern String are under-specified and there are undocumented exceptions.

The wording for `getLimits()` and `getFormats()` was also adjusted, as there are other ways to set the limits and formats beyond the constructor.

The changes may be easier to view -> https://cr.openjdk.org/~jlu/api/java.base/java/text/ChoiceFormat.html

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Commit messages:
 - Clarify ≤
 - Adjust pattern definition
 - Remove leftover comments
 - Revert the example changes to focus on the more important changes
 - Adjust wording of getter methods
 - Init

Changes: https://git.openjdk.org/jdk/pull/15392/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15392&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-6228794
  Stats: 69 lines in 1 file changed: 46 ins; 7 del; 16 mod
  Patch: https://git.openjdk.org/jdk/pull/15392.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15392/head:pull/15392

PR: https://git.openjdk.org/jdk/pull/15392