Expose CredentialManager UI result propagation interfaces as System APIs

The APIs exposed will be used by the CredentialManager UI activity to
send the UI success / failure results back to the system service. The
entry points are defined in ResultHelper.java and the rest are data
classes.

Test: CTS test & local build
Bug: 322065247
Change-Id: I8bd2375f046866caf87d69b90502414e14e2b879