hg: shenandoah/jdk11: Shenandoah: enable low-frequency STW class unloading

[shade at redhat.com]

Changeset: 1def25c0a60e
Author:    shade
Date:      2020-07-20 16:05 +0200
URL:       https://hg.openjdk.java.net/shenandoah/jdk11/rev/1def25c0a60e

Shenandoah: enable low-frequency STW class unloading

! src/hotspot/share/gc/shenandoah/shenandoahArguments.cpp
! src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp
! test/hotspot/jtreg/gc/shenandoah/options/TestClassUnloadingArguments.java