RFR: 8307953: [AIX] C locale's font setting was changed by JEP 400

[Ichiroh Takiguchi]

On AIX, lib/fontconfig.bfc file is used to find font setting.
I ran SwingSet2 List demo program with AIX C locale.
JDK21's line spacing is larger then JDK17.
Screen shots are in [JDK-8307953](https://bugs.openjdk.org/browse/JDK-8307953).
When I used `-Dfile.encoding=COMPAT` option on AIX C locale, SwingSet2 worked fine as expected.

This situation happens `Charset.defaultCharset()` always returns UTF-8 after JEP 400 by default.
`native.encoding` system property has platform's encoding/charset name.
If platform's charset name is not supported by Java, charset name should be `UTF-8`.

Additionally, following parts are changed:
`src/java.desktop/aix/data/fontconfig/fontconfig.propertie`s has invalid charset name.
For Java for AIX:
- Encoding name for AIX's Zh_TW locale is `big5`, charset name should be `x-IBM950` instead of `big5`.
- Encoding name for AIX's zh_CN locale is `IBM-eucCN`, charset name should be `x-IBM1383` instead of `x-EUCCN`.

In my understanding, this fix affects just for AIX platform.

Note:
macos-x64 tier1 test was failed, but I think it's not related this PR.

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

Commit messages:
 - 8307953: [AIX] C locale's font setting was changed by JEP 400

Changes: https://git.openjdk.org/jdk/pull/13937/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13937&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307953
  Stats: 7 lines in 2 files changed: 3 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/13937.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13937/head:pull/13937

PR: https://git.openjdk.org/jdk/pull/13937