RFR: 8308108: Support Unicode extension for collation settings [v4]

[Naoto Sato]

> This change intends to interpret the BCP47 U extension wrt collation settings in the given `Locale`, then applies them to the created instances in the 1-arg factory method in `Collator`. A corresponding CSR has also been drafted.

Naoto Sato has updated the pull request incrementally with one additional commit since the last revision:

  A bit of clarification

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Changes:
  - all: https://git.openjdk.org/jdk/pull/14040/files
  - new: https://git.openjdk.org/jdk/pull/14040/files/627b78b3..1cfc09b6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14040&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14040&range=02-03

  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/14040.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14040/head:pull/14040

PR: https://git.openjdk.org/jdk/pull/14040