moved key_derivation.rs from pbs_datastore to pbs-config/src/key_config.rs

Also moved pbs-datastore/src/crypt_config.rs to pbs-tools/src/crypt_config.rs.
We do not want to depend on pbs-api-types there, so I use [u8;32] instead of
Fingerprint.

pbs-datastore/src/checksum_reader.rs

@@ -3,8 +3,7 @@ use std::sync::Arc;
 use std::io::Read;
 
 use pbs_tools::borrow::Tied;
-
-use super::CryptConfig;
+use pbs_tools::crypt_config::CryptConfig;
 
 pub struct ChecksumReader<R> {
     reader: R,