Add RecoverableKeyStoreLoader implementation in LockSettingsService.

1) Updates to ILockSettings.aidl
Since we can't pass arbitrary exception using IPC, Serrvice
converts them to ServiceSpecificException with an error code.

2) Added RecoverableKeyStoreManager class which is used as interface
between RecoverableKeyStoreLoader implementation and
LockSettingsService.

Test: none
Bug: 66499222

Change-Id: I03b695bc0ced1a91ea7ca5de179e121053dfe416