[feature/crypto] Do not check if type_map is empty

If the type map is empty the service container is incomplete or broken.
There is no need to check this as other components would probably be broken
at the same time.

PHPBB3-11610
[feature/crypto] NULL should be null according to coding guidelines

PHPBB3-11610
[feature/crypto] Do not use specific errors but rather just return false

The authentication system should handle the possible errors for now.
Additional error returns can be added later on if they are needed.

PHPBB3-11610
[feature/crypto] Increase manager test coverage to cover all methods

All methods in the crypto manager are now fully covered.

PHPBB3-11610