<i18n dev> RFR: 8289227: Support for BCP 47 Extension T - Transformed Content [v2]

[Naoto Sato]

> This PR is to propose supporting the `T` extension to the BCP 47 to which `java.util.Locale` class conforms. There are two extensions to the BCP 47, one is `Unicode Locale Extension` which has been supported since JDK7, the other is this `Transformed Content` extension. A CSR has also been drafted.

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

  Removed unnecessary `contains()` check

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9620/files
  - new: https://git.openjdk.org/jdk/pull/9620/files/1f1526bc..a869efaa

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9620&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9620&range=00-01

  Stats: 5 lines in 3 files changed: 0 ins; 3 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/9620.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9620/head:pull/9620

PR: https://git.openjdk.org/jdk/pull/9620