DTFJ parser doesn't detect javacore thread stacks for matching PHD

[kgibm]

MAT has a bit of an obscure feature where it can augment a DTFJ PHD dump with thread stacks (PHDs don't have thread stacks built-in) if MAT finds a matching javacore file in the same directory: https://help.eclipse.org/latest/topic/org.eclipse.mat.ui.help/tasks/acquiringheapdump.html

By loading in both a javacore.txt file (IBM thread dump file) and a heapdump.phd file that were generated at the same time, Memory Analyzer makes thread details available in the IBM PHD format dump.

I don't often use PHDs but someone had a PHD and tried this function and it didn't seem to work. I can reproduce this on a public example PHD and javacore: https://github.com/IBM/webspherelab/tree/main/supplemental/exampledata/liberty/verbosegc_and_oom

Not a big issue so not very high priority, but just wanted to document it. Also worth noting that the javacore and PHD are taken at slightly different times, so this feature shouldn't be relied on too strongly anyway. Core dumps are generally recommended over PHDs as they're a superset, have thread stacks built-in, etc.