BIO_f_cipher(): Increase internal buffer size used by CipherUpdate()

BIO_f_cipher(): Increase internal buffer size used by CipherUpdate()

Previously running the commandline "openssl enc -id-aes256-wrap-pad ...'
with a large PQ private key failed since AES-WRAP is not streamable,
and multiple calls to CipherUpdate() are not allowed. Increasing the
size causes CipherUpdate() to only be called once.
The size of the buffer has been changed from 4K to 8K.

Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/29940)