ci: split up aead tests

[dougch]

Goal

Speed up the slowest unit test(s).

Why

The aead-aes test is significantly slower than the next slowest test.

How

Split it into two, based on ciphers and pull any repeatable code into a utilities header.

These currently run serially, totaling around 16 minutes (valgrind with OSSL30-FIPS). By separating them, they run in parallel, with the longer pole (256) finishing in about 8 minutes.

Testing

CI

Related

resolves https://github.com/aws/s2n-tls/issues/4472

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.