RFR: JDK-8320309: AIX: pthreads created by foreign test library don't work as expected

[Varada M]

Following test fails due to missing pthread attributes on AIX :
java/foreign/TestUpcallAsync.java
java/foreign/stackwalk/TestAsyncStackWalk.java
java/foreign/loaderLookup/TestLoaderLookupJNI.java
java/foreign/enablenativeaccess/TestEnableNativeAccessJarManifest.java
java/foreign/enablenativeaccess/TestEnableNativeAccess.java

Note : Test needs the changes from [pull/16579](https://github.com/openjdk/jdk/pull/16579) and [pull/16414](https://github.com/openjdk/jdk/pull/16414 )

JBS Issue : [JDK-8320309](https://bugs.openjdk.org/browse/JDK-8320309)

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Commit messages:
 - added pthread_attr_destroy
 - added pthread attributes

Changes: https://git.openjdk.org/jdk/pull/16757/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16757&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8320309
  Stats: 6 lines in 1 file changed: 5 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16757.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16757/head:pull/16757

PR: https://git.openjdk.org/jdk/pull/16757