Add Cipher support to autodocs.

Ciphers are more complicated than other categories because providers can
declare that they provide a base algorithm but users request an
algorithm/mode/padding triple, so we need to investigate the possible
values of that triple and see which ones actually end up available.

We ignore all the PBE ciphers because they're a mess and we don't
want them to show up in the documentation.

The starting API level for AES/GCM/NOPADDING is actually an educated
guess, it's approximately correct but might be off by one or two.
I'll update it if I later get better information.

Bug: 35793879
Test: Ran run_update_crypto_support.sh
Change-Id: Ifb827818626690ff223f691c8297731790074283