Remove support for the algorithms deprecated in r348876.

This removes support for the following algorithms:

• ARC4
• Blowfish
• CAST128
• DES
• 3DES
• MD5-HMAC
• Skipjack

Since /dev/crypto no longer supports 3DES, stop testing the 3DES KAT
vectors in cryptotest.py.

Reviewed by: cem (previous version)
Relnotes: yes
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D24346