<i18n dev> RFR: 8300706: Use @snippet in java.text

[Justin Lu]

Some classes / interfaces in java.text have already implemented JEP 413.

This PR implements _JEP 413: Code Snippets in Java API Documentation_ for the rest of [java.text](https://docs.oracle.com/en/java/javase/19/docs/api/java.base/java/text/package-summary.html) including:
- BreakIterator
- CharacterIterator
- DateFormatSymbols
- DecimalFormat
- NumberFormat 

Code examples using <pre> ... </pre> blocks are replaced with the @ snippet syntax where applicable.

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Commit messages:
 - Snippet for NFormat
 - DecimalFormat changes
 - Example in DFSymbols should end with semicolon
 - Snippet for DFSymbols
 - Minor spacing in CIterator
 - Snippet for CIterator
 - Snippet for BIterator

Changes: https://git.openjdk.org/jdk/pull/12121/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12121&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8300706
  Stats: 43 lines in 5 files changed: 1 ins; 0 del; 42 mod
  Patch: https://git.openjdk.org/jdk/pull/12121.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12121/head:pull/12121

PR: https://git.openjdk.org/jdk/pull/12121