Move token persistence classes to token.persistence module

Create and move all token persistence code to a new token.persistence
module. This allows the token_provider_api to utilize the token
persistence service without introducing circular dependencies. A proxy
class, that will log a deprecation message if instantiated, has been
created for both the token.core.Manager object and token.core.Driver
object. These proxy objects are slated for removal in the K cycle.

Change-Id: Iae1240c6de4382332b967926efe31f5355554f6e
bp: non-persistent-tokens
Merge "Move token persistence classes to token.persistence module"