Consolidate jobs into single steps instead of branching out

[zhilingc]

The current ingestion job graph is built such that each distinct feature set has its own subgraph; branching is done by tagging each incoming feature row.

This has resulted in the following 2 problems:

1. With large amounts of features the graph balloons in size - so much so that the job is unable to be submitted to dataflow.
2. Inability to update jobs with metrics enabled, since the type for the metrics step is changed between updates

This PR consolidates the steps such that all feature rows follow the same path through the graph.

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[zhilingc]

/retest

[zhilingc]

/retest

[zhilingc]

/retest

[woop]

/lgtm