[lworld] RFR: 8355614: [lworld] SIGSEGV in InlineKlass::write_value_to_addr

[Tobias Hartmann]

We crash in `InlineKlass::write_value_to_addr` when writing to a field that is not a flat field. The root cause is that `b->layout_kind() == LayoutKind::NULLABLE_ATOMIC_FLAT` is true in `FieldLayout::shift_fields` because `_layout_kind` contains garbage. It needs to be initialized in the constructor.

I also fixed a few other minor things.

Thanks,
Tobias

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Commit messages:
 - 8355614: [lworld] SIGSEGV in InlineKlass::write_value_to_addr

Changes: https://git.openjdk.org/valhalla/pull/1472/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1472&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8355614
  Stats: 14 lines in 5 files changed: 5 ins; 3 del; 6 mod
  Patch: https://git.openjdk.org/valhalla/pull/1472.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1472/head:pull/1472

PR: https://git.openjdk.org/valhalla/pull/1472