Fix EVP_Cipher() for provided cipher implementations

Fix EVP_Cipher() for provided cipher implementations

EVP_Cipher() would return whatever ctx->cipher->ccipher() returned
with no regard for historical semantics.

We change this to first look if there is a ctx->cipher->ccipher(), and
in that case we treat the implementation as one with a custom cipher,
and "translate" it's return value like this: 0 => -1, 1 => outl, where
|outl| is the output length.

If there is no ctx->cipher->ccipher, we treat the implementation as
one without a custom cipher, call ctx->cipher->cupdate or
ctx->cipher->cfinal depending on input, and return whatever they
return (0 or 1).

Furthermore, we add a small hack in EVP_CIPHER_flags() to check if the
cipher is a provided one, and add EVP_CIPH_FLAG_CUSTOM_CIPHER to the
flags to be returned if there is a cipher->ccipher.  That way,
provided implementations never have to set that flag themselves, all
they need to do is to include a OSSL_FUNC_CIPHER_CIPHER function.

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/10137)