Python: add py3-headers target to support compiled python modules am: 8ae4cfb5a0 am: ad98b5ec45

Original change: https://android-review.googlesource.com/c/platform/external/python/cpython3/+/3478370

Change-Id: Ie7d4f4c4aa17234f9016075b8bd18aa3cd007251
Signed-off-by: Automerger Merge Worker <[email protected]>