Add the ability to get information about tasks completed so far from sources, transformers, and sinks

[yruslan]

Background

This feature is needed so that a job can determine if schema has changed during the execution of the dependent job.

Feature

Add the ability to get information about tasks completed so far from sources, transformers, and sinks.

Example

--

Proposed Solution

Extend Pramen trait to get the current state of the pipeline.