Shenandoah: fix Shenandoah Loom support

java/lang/Thread/virtual/stress/Skynet.java test failed with loom.

To reproduce:
 make CONF=linux-x86_64-server-fastdebug TEST_VM_OPTS="--enable-preview -XX:+UseShenandoahGC" run-test TEST=java/lang/Thread/virtual/stress/Skynet.java


# Internal Error (/home/zgu/ws/jdk/src/hotspot/share/oops/compressedOops.inline.hpp:135), pid=3328186, tid=3328207
# assert(check_alignment(result)) failed: address not aligned: 0x00000008baadbabe
#
# JRE version: OpenJDK Runtime Environment (19.0) (fastdebug build 19-internal-adhoc.zgu.jdk)
# Java VM: OpenJDK 64-Bit Server VM (fastdebug 19-internal-adhoc.zgu.jdk, mixed mode, sharing, tiered, compressed oops, compressed class ptrs, shenandoah gc, linux-amd64)
# Problematic frame:
# V [libjvm.so+0x190f877][thread 3328211 also had an error]
  ShenandoahAsserts::assert_correct(void*, oop, char const*, int)+0x987