git: openjdk/loom: fibers: Temporarily fix to disable enumerateVThreads and now block VIRTUAL_THREAD_START event

[duke]

Changeset: 48cfaf20
Author:    Alan Bateman <alan.bateman at oracle.com>
Date:      2021-03-19 11:15:24 +0000
URL:       https://git.openjdk.java.net/loom/commit/48cfaf20

Temporarily fix to disable  enumerateVThreads and now block VIRTUAL_THREAD_START event

! src/hotspot/share/prims/jvmti.xml
! src/jdk.jdwp.agent/share/native/libjdwp/ThreadGroupReferenceImpl.c
! src/jdk.jdwp.agent/share/native/libjdwp/debugInit.c
! src/jdk.jdwp.agent/share/native/libjdwp/eventHandler.c