RFR: 8310683: Refactor StandardCharset/standard.java to use JUnit [v4]

[Justin Lu]

> 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 with a new target base due to a merge or a rebase. The pull request now contains five commits:

 - Merge branch 'pr/14599' of https://git.openjdk.org/jdk into JUnit-StandardCharsets
 - Merge pr/14599
 - Additional cleanup
 - Refactor Standard.java to use JUnit + other cleanup
 - Fix imports and update copyright year

-------------

Changes: https://git.openjdk.org/jdk/pull/14621/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14621&range=03
  Stats: 118 lines in 1 file changed: 31 ins; 20 del; 67 mod
  Patch: https://git.openjdk.org/jdk/pull/14621.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14621/head:pull/14621

PR: https://git.openjdk.org/jdk/pull/14621