Stop job run model caring about update types

[patchwork01]

Background

Split from:

• Remove start of run flag from ingest job tracker #4256

In JobRun.Builder.statusUpdate, we currently check the type of the update so that we can report on whether the job is finished and give a summary of the run. This includes calling JobRunStartedUpdate.isStartOfRun, which we want to remove.

Description

We'd like to remove the type checks in JobRun, and make this type detection specific to ingest and compaction instead. That way we can be more explicit about the differences between an ingest job run and a compaction job run.

This should also make it more feasible to remove JobRunStartedUpdate.isStartOfRun, as in the linked issue.

Analysis

We can create a CompactionJobRun and an IngestJobRun, and return those from CompactionJobStatus and IngestJobStatus instead of JobRun.