Compare new unwinder to old unwinder in debuggerd.

In debuggerd, when dumping a tombstone, run the new unwinder and verify
the old and new unwinder are the same. If not, dump enough information
in the tombstones to figure out how to duplicate the failure.

Bug: 23762183

Test: Builds, ran and forced a mismatch and verified output.
Change-Id: Ia178bde64d67e623d4f35086ebda68aebbff0c3c