<i18n dev> RFR: 8347955: TimeZone methods to stream the available timezone IDs

[Justin Lu]

Please review this PR and CSR which add a pair of methods to _java.util.TimeZone_ that return a stream of the available IDs. See the CSR for the motivation.

A number of existing tests are modified to use the new methods. See _test/jdk/java/util/TimeZone/AvailableIDsTest.java_ which tests the new methods.

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Commit messages:
 - space at EOF
 - test
 - src

Changes: https://git.openjdk.org/jdk/pull/23251/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23251&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8347955
  Stats: 177 lines in 15 files changed: 146 ins; 3 del; 28 mod
  Patch: https://git.openjdk.org/jdk/pull/23251.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23251/head:pull/23251

PR: https://git.openjdk.org/jdk/pull/23251