tests/krb5/s4u_tests.py: add test_constrained_delegation_authtime

tests/krb5/s4u_tests.py: add test_constrained_delegation_authtime

This demonstrates that we use the correct authtime
when doing constrained delegation.

The actual fix for the problem is already in place via
commit 75ec66c729faad60fa18b9504ba4053b3e2f47bc
third_party/heimdal: Import lorikeet-heimdal-202306091507 (commit 7d8afc9d7e3d309ddccc2aea6405a8ca6280f6de)

The related patch is:
006a365a6aa3047a4e685e1607973746a28cc1f1 kdc: use the correct authtime from addtitional ticket for S4U2Proxy tickets

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13137

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>