bpo-29590: fix stack trace for gen.throw() with yield from (GH-19896)

* Add failing test.

* bpo-29590: fix stack trace for gen.throw() with yield from (GH-NNNN)

When gen.throw() is called on a generator after a "yield from", the
intermediate stack trace entries are lost.  This commit fixes that.
(cherry picked from commit 8b33961e)

Co-authored-by: Chris Jerdonek <chris.jerdonek@gmail.com>