Revert "Add and use Throwable.UNASSIGNED_STACK from upstream 8u121-b13"

This reverts commit 40120088de64b1610da646e5ff5304d1e620a3b7.

Reason for revert: Appears to break Serialization of some Throwable subclasses.

Bug: 35910877
Bug: 109930347
Change-Id: I0ea1596152c2fd622db95477f1d531366956736f
4 files changed