8362257: (process) Remove aliveness-ping-workaround for older glibcs in POSIX_SPAWN mode

[tstuefe]

Removes the liveness ping since it is not needed anymore for newer versions of glibc.

See JBS issue description for more details, and also for analysis of the major Linux distros wrt glibc version.

Patch also removes throwExitCause(), introduced with https://bugs.openjdk.org/browse/JDK-8226242 to analyze pre-exec abnormal abortions in jspawnhelper (see discussion about that removal at https://mail.openjdk.org/pipermail/core-libs-dev/2025-July/148908.html).

We then can also remove the definitions for the waitpid status macros (WIFSIGNALED and so forth). These were remnants from the initial checkin, back at that time used for Java_java_lang_UNIXProcess_waitForProcessExit. That one has long been moved.

In Java_java_lang_ProcessImpl_forkAndExec, I modified the error-number-printout to preserve the specialized printout for jspawnhelper error codes introduced by Aleksey with JDK-8352533.

Note: removing this code also fixes a path that would have caused Zombie processes to appear (see https://bugs.openjdk.org/browse/JDK-8362267 , which is a separate issue).

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Issue

• JDK-8362257: (process) Remove aliveness-ping-workaround for older glibcs in POSIX_SPAWN mode (Enhancement - P4) ⚠️ Issue is not open.

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