Start integraring encryption and compression so that we have
only one implementation of encryption using CRYPT_SCHEME_1
where

L = AES_ECB(KEY, IV)
CRYPT(PAGE) = AES_CRT(KEY=L, IV=C, PAGE)

and two different implementations how keys are stored.

For AIO this means that compression and encryption is called
at os0file as earlier. For all other we do these at buf0buf.cc.