RFR: 8310683: Refactor StandardCharset/standard.java to use JUnit [v5]

[Naoto Sato]

On Fri, 23 Jun 2023 20:45:14 GMT, Justin Lu <jlu at openjdk.org> wrote:

>> Please review this PR which is apart of the migration of JDK tests to JUnit. Standard.java is refactored to use JUnit, and thus split up into the following tests.
>> 
>> - typeTest
>> - nameMethodTest
>> - forNameMethodTest
>> - charsetModifiersTest
>> - correctCharsetsTest
>> 
>>  Additionally all unused methods were removed.
>
> Justin Lu has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Just use charsetFields()
>  - Review: reuse the standard charset fields

Marked as reviewed by naoto (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/14621#pullrequestreview-1496024461