RFR: 8329222: java.text.NumberFormat (and subclasses) spec updates [v4]

[Justin Lu]

> Please review this PR which is a large spec reformatting for _java.text.NumberFormat_ and related subclasses, specifically DecimalFormat and CompactNumberFormat.
> 
> The motivation for this change was the difficulty of readability for these classes. This PR consists of changes such as better separating the text into sections with headers, advising to skip the pattern related sections if not needed, and general wording improvements.
> 
> To help with reviewing I have attached a [specdiff](https://cr.openjdk.org/~jlu/JDK-8329222/java.base/java/text/package-summary.html) as well as the built docs: [nFmt](https://cr.openjdk.org/~jlu/api/java.base/java/text/NumberFormat.html), [dFmt](https://cr.openjdk.org/~jlu/api/java.base/java/text/DecimalFormat.html), and [cnFmt](https://cr.openjdk.org/~jlu/api/java.base/java/text/CompactNumberFormat.html);
> 
> I will update the CSR once the wording is finalized.

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

  Make apparent the distinction of cnFmt and dFmt for factory methods.
  Loosen wording from cast to convert.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18731/files
  - new: https://git.openjdk.org/jdk/pull/18731/files/95626d94..33b02f00

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18731&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18731&range=02-03

  Stats: 10 lines in 3 files changed: 0 ins; 1 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/18731.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18731/head:pull/18731

PR: https://git.openjdk.org/jdk/pull/18731