crypto: deduplicate cipher initialization code

CipherBase::Init and CipherBase::InitIv contain a lot of duplicate
code, this commit moves that into a separate function.

PR-URL: https://github.com/nodejs/node/pull/23011


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>