<i18n dev> RFR: 8258795: Update IANA Language Subtag Registry to Version 2021-05-11

[Naoto Sato]

Please review the changes to the subject issue. This is to incorporate the latest language subtag registry definition into the JDK.

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Commit messages:
 - Renaming the test case
 - LSR 2021-05-11
 - LSR 2021-03-05
 - LSR 2021-02-23
 - LSR 2020-12-18

Changes: https://git.openjdk.java.net/jdk/pull/3998/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3998&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8258795
  Stats: 340 lines in 2 files changed: 327 ins; 0 del; 13 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3998.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3998/head:pull/3998

PR: https://git.openjdk.java.net/jdk/pull/3998