[jdk8u-ri] RFR: 8305681: Allow additional characters for GB18030-2022 (Level 2) support

[Naoto Sato]

This is to support GB18030-2022 "Implementation Level 2", an extension to JDK-8301400. Additional 108 code points from `CJK Unified Ideographs Extension E` block in Unicode 8.0 need to be allowed.

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Commit messages:
 - Fixed CheckScript.java
 - Merge pull request #1 from justin-curtis-lu/JSR337-MR5-L2-TestChanges
 - Clarify variable names and comments
 - Update level 2 code points to include entire Extension E block
 - Clarify wording for supplementary characters
 - wording
 - Update test for CJK_E code points
 - 8305686: Allow additional characters for GB18030-2022 (Level 2) support

Changes: https://git.openjdk.org/jdk8u-ri/pull/13/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk8u-ri&pr=13&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305681
  Stats: 54 lines in 6 files changed: 37 ins; 0 del; 17 mod
  Patch: https://git.openjdk.org/jdk8u-ri/pull/13.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-ri.git pull/13/head:pull/13

PR: https://git.openjdk.org/jdk8u-ri/pull/13