java/foreign/TestLargeSegmentCopy.java failed on aix with jdk20

java/foreign/TestLargeSegmentCopy.java failed on aix with jdk20. Test was added last December. https://github.com/openjdk/jdk20/blob/master/test/jdk/java/foreign/TestLargeSegmentCopy.java

https://ci.adoptium.net/job/Test_openjdk20_hs_sanity.openjdk_ppc64_aix/62/console
```
01:14:56 test TestLargeSegmentCopy.testLargeSegmentCopy(): failure
01:14:56 java.lang.OutOfMemoryError: Unable to allocate 2147484504 bytes
01:14:56 at java.base/jdk.internal.misc.Unsafe.allocateMemory(Unsafe.java:632)
01:14:56 at java.base/jdk.internal.foreign.NativeMemorySegmentImpl.makeNativeSegment(NativeMemorySegmentImpl.java:116)
01:14:56 at java.base/java.lang.foreign.MemorySegment.allocateNative(MemorySegment.java:1251)
01:14:56 at TestLargeSegmentCopy.testLargeSegmentCopy(TestLargeSegmentCopy.java:49)
01:14:56 at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
01:14:56 at java.base/java.lang.reflect.Method.invoke(Method.java:578)
```

Suspect doesn't work AIX as segment is too large and out of memory.

Start with test/jdk/java/foreign/TestLargeSegmentCopy.java, especially the allocation at TestLargeSegmentCopy.java:49, and review the linked AIX CI failure. Confirm why the large native segment allocation fails on AIX and determine an appropriate test change. Done means the test passes on AIX while still checking large-segment copying behavior.

Written by the indexing model from the issue text.