RFR: 6228794: java.text.ChoiceFormat pattern behavior is not well documented. [v7]

[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.
> 
> The wording for `getLimits()` and `getFormats()` was also adjusted, as there are other ways to set the limits and formats beyond the constructor.
> 
> The pattern syntax may be easier to view -> https://cr.openjdk.org/~jlu/api/java.base/java/text/ChoiceFormat.html

Justin Lu has updated the pull request incrementally with one additional commit since the last revision:

  Use <d_> description tags to create syntax, include negative symbol in Number section

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15392/files
  - new: https://git.openjdk.org/jdk/pull/15392/files/216e5ac7..ff1be6ad

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15392&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15392&range=05-06

  Stats: 53 lines in 1 file changed: 30 ins; 0 del; 23 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