git: openjdk/loom: fibers: Get rid of SA support for ThreadGroups. It wasn't being used by any tool, and doesn't work properly now that ThreadGroup no longer keeps track of all threads in the group.

[duke]

Changeset: 616bb69c
Author:    Chris Plummer <chris.plummer at oracle.com>
Date:      2022-03-19 18:26:10 +0000
URL:       https://git.openjdk.java.net/loom/commit/616bb69ca06101de1d81c3bd40a09ded733f7ddb

Get rid of SA support for ThreadGroups. It wasn't being used by any tool, and doesn't work properly now that ThreadGroup no longer keeps track of all threads in the group.

! src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/memory/SystemDictionary.java
! src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/oops/OopUtilities.java