Although RSA can be used directly for signing / JWS
on large chunks of data since it's only operating on
the hash, when JWE support arrives, which allows bulk
encryption, it's going to be mandatory to support
secondary AES ciphers to use on the bulk data.
This adds generic support for all AES modes that OpenSSL
and mbedTLS have in common, works on both mbedTLS and
OpenSSL the same, and adds unit tests for each mode
in api-test-gencrypto, to run in CI.
Until now the JOSE pieces only had enough support for ACME.
This patch improves the JWK parsing to prepare for more
complete support and for adding JWE, genaes and genec in
later patches.
