<i18n dev> RFR: 8300589: Use @snippet and @linkplain in java.text.CollationKey and java.text.CompactNumberFormat

[Justin Lu]

This PR implements _JEP 413: Code Snippets in Java API Documentation_ for [java.text.CollationKey](https://docs.oracle.com/en/java/javase/19/docs/api/java.base/java/text/CollationKey.html) and [java.text.CompactNumberFormat](https://docs.oracle.com/en/java/javase/19/docs/api/java.base/java/text/CompactNumberFormat.html).

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

Additionally, for [java.text.CompactNumberFormat](https://docs.oracle.com/en/java/javase/19/docs/api/java.base/java/text/CompactNumberFormat.html) internal plain text links using <a> ... </a> are replaced with @ linkplain. (External links are kept the same)

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Commit messages:
 - Use linkplain for plain text internal links
 - Swap to snippet

Changes: https://git.openjdk.org/jdk/pull/12108/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12108&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8300589
  Stats: 15 lines in 2 files changed: 0 ins; 0 del; 15 mod
  Patch: https://git.openjdk.org/jdk/pull/12108.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12108/head:pull/12108

PR: https://git.openjdk.org/jdk/pull/12108