JDK8: Two failing charset tests (IBM943) in the NIO suite on some systems

The following two tests fail on Amazon Linux 2023 but it's not limited to that platform (Verified on Debian12 and Ubuntu 24.04):

- [sun/nio/cs/TestCharsetMapping.java](https://ci.adoptium.net/job/Grinder/10264/testReport/sun_nio_cs_TestCharsetMapping/) - Not immediately obvious which is causing the real failure as there are a few "Error" references but it could be:
```
testing: x-IBM943
string de/encoding
new String()
String.getBytes()
1 byte/char
decode
decode (direct)
2 bytes/char
decode
decode (direct)
1 byte/char
encode
encode (direct)
2 bytes/char
encode
Error: U+8ec0 --> 3f3f, expected 8beb
Error: U+8141 --> 3f3f, expected e445
Error: U+6805 --> 3f3f, expected 8df2
Error: U+7006 --> 3f3f, expected 93c0
Error: U+8346 --> 3f3f, expected 8c74
Error: U+7e48 --> 3f3f, expected e379
Error: U+840a --> 3f3f, expected 9789
Error: U+56ca --> 3f3f, expected 9458
Error: U+ff0d --> 3f3f, expected 817c
Error: U+688e --> 3f3f, expected 9e94
Too many errors, giving up
encode (direct)
Error: U+8ec0 --> 3f3f, expected 8beb
Error: U+8141 --> 3f3f, expected e445
Error: U+6805 --> 3f3f, expected 8df2
Error: U+7006 --> 3f3f, expected 93c0
Error: U+8346 --> 3f3f, expected 8c74
Error: U+7e48 --> 3f3f, expected e379
Error: U+840a --> 3f3f, expected 9789
Error: U+56ca --> 3f3f, expected 9458
Error: U+ff0d --> 3f3f, expected 817c
Error: U+688e --> 3f3f, expected 9e94
Too many errors, giving upThe
```
- sun/nio/cs/TestIBMBugs.java - the failure here would be consistent with the error above with an IBM943 encoding failure:
```
java.lang.Exception: x-IBM943 failed to encode
at TestIBMBugs.bug8235834(TestIBMBugs.java:225)
at TestIBMBugs.main(TestIBMBugs.java:242)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.sun.javatest.regtest.agent.MainActionHelper$AgentVMRunnable.run(MainActionHelper.java:298)
at java.lang.Thread.run(Thread.java:750)

JavaTest Message: Test threw exception: java.lang.Exception
JavaTest Message: shutting down test
```

Start with sun/nio/cs/TestCharsetMapping.java and sun/nio/cs/TestIBMBugs.java, then reproduce the x-IBM943 failures on the reported Linux systems. Trace the encoding mismatch shown in the test output and verify that both tests pass across the affected environments.

Written by the indexing model from the issue text.