RFR: 8203290: [PPC64, s390] Check functionality of JDK-8199712 (Flight Recorder) [v15]

[Tyler Steele]

> Just in time for the holidays I have completed an implementation of the JFR functionality for AIX. As a side note, this is my first submission to OpenJDK 👋
> 
> ### Implementation notes and alternatives considered
> 
> After modifying the build system to allow the --enable-jvm-feature-jfr to work on AIX, my task was to implement the interfaces from os_perf.hpp. The os_perf_aix.cpp implementation that existed was, I believe, a copy of the Linux implementation. A review of the code in that file showed that NetworkInterface, CPUPerformanceInterface, and SystemProcessInterface would require modification to work on AIX. Using the Linux implementation as a guide, I initially expected to use files from the aix procfs like /proc/<pid>/psinfo, and /proc/<pid>/status in a manner similar to the Linux implementation. However, I ended up using libperfstat for all functionality required by the interfaces.
> 
> ### Testing
> 
> Testing for JFR seems to be quite light in the repo both before and after this change. In addition to performing manual testing, I have added some basic sanity checks that ensure events can be created and committed (using jtreg), and performs some basic checks on the results of the interface member functions (using gtest).
> 
> ### More notes
> 
> I've sent an email to the JFR group about a TOC overflow warning I encountered while building (for the release server target). I believe the fix is to pass -qpic=large when using the xlc toolchain, but my modifications to flags-cflags.m4 have not been successful in removing this warning.

Tyler Steele has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains two commits:

 - Merge branch 'master' into JDK-8203290
 - Implements JFR on AIX
   
   - Implements interfaces from os_perf.hpp in os_perf_aix.cpp
   - Updates libperfstat_aix to contain functionality needed by os_perf_aix
   - Implements missing functionality in loadlib_aix (Fixes failure noted
   by TestNativeLibraies.java)
   - Removes platform checks for --enable-feature-jfr (Now enable-able on
   all platforms)
   - Enables TestNetworkUtilizationEvent.java which now passes on AIX
   - Updates AIX JavaThread::pd_get_top_frame_for_profiling with changes from Linux

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Changes: https://git.openjdk.java.net/jdk/pull/6885/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6885&range=14
  Stats: 1186 lines in 10 files changed: 495 ins; 477 del; 214 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6885.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6885/head:pull/6885

PR: https://git.openjdk.java.net/jdk/pull/6885