jdk8u backport is brokent in 1.8.0.232.b09

[Алексей Генус]

Hello, Shenandoah devs.
I updated jdk8 from 191-b12 to 232-b09 and started to get spurious freezes
of my application during startup which occur pretty consistently. Digging
into gave me impression that is something wrong with java itself. Having
tried to use fastdebug build I started to get these hs_err.logs:
https://gist.github.com/genuss/e1969c081f7656ea14e992d84dc8a180
https://gist.github.com/genuss/310b67fc3f1f49b458c0e13f13b67fdd
and another possible outcome is same as earlier - hung jvm which heavily
consumes CPU in GC threads with a stacktrace like that (got it with perf):
32.32%  libjvm.so     [.] ShenandoahAsserts::assert_correct
16.16%  libjvm.so     [.] ShenandoahBarrierSet::write_barrier
10.10%  libjvm.so     [.] JvmtiTagMap::do_weak_oops
8.43%  libjvm.so      [.] ShenandoahForwardedIsAliveClosure::do_object_b
8.25%  libjvm.so      [.]
ShenandoahEvacuateUpdateRootsClosure::do_oop_work<oop>
6.71%  libjvm.so      [.] ShenandoahHeap::in_collection_set<oop>
6.16%  libjvm.so      [.] ShenandoahHeap::is_in
5.53%  libjvm.so      [.] Metaspace::contains
2.70%  libjvm.so      [.] ShenandoahHeap::heap
2.43%  libjvm.so      [.] ShenandoahHeap::kind
0.76%  libjvm.so      [.] ShenandoahHeap::heap_no_check
0.24%  [kernel]       [k] trigger_load_balance
0.14%  [kernel]       [k] system_call_fastpath

Aleksey Shipilev suggested running on latest shenandoah-backport. I did it
and it gave me another error in 100% cases (probably unrelated to original
error). The log is here
https://gist.github.com/genuss/10eae7f6cc41e9ea1c59ca723915353b

Moving back to 1.8.0.192 helps, but maybe we can find the error here.
Unfortunately I don't haven a minimal reproducible example, but I'm open to
any suggestions on how to make it.
Do you have any thoughts about how to fix this?

Alexey