RFR: 8301119: Support for GB18030-2022 [v4]

[Lance Andersen]

On Fri, 24 Feb 2023 17:23:25 GMT, Naoto Sato <naoto at openjdk.org> wrote:

>> Upgrading the GB18030 charset in the JDK to the latest 2022 standard. Since this is not a compatible upgrade to the existing mapping, a new system property `jdk.charset.GB18030` is introduced. If it is set to "2000", the mapping falls back to the existing mapping based on the 2000 standard, otherwise, it defaults to 2022 mapping. Refer to the corresponding CSR for more detail.
>
> Naoto Sato has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Failed to add the file itself
>  - Changed GB18030 from extcs template to stdcs source

Marked as reviewed by lancea (Reviewer).

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PR: https://git.openjdk.org/jdk/pull/12518