Use JobManager's backend as persistent storage and source of truth - #903

What this PR does / why we need it:

As part of the plan to decouple JobCoordinator & Core and eventually move Job Management to dedicated service this PR is the first step in this direction.

JobCoordinator doesn't rely on any persistent storage anymore. We store temporary state in memory (see InMemoryJobRepository) and fetch this state each time application is being started (see JobManager.listJobs).

For DataflowJobManager it means that we fetch list of jobs directly from Dataflow. We distinguish jobs that are being managed by current application by job's labels (see property feast.jobs.coordinator.jobSelector). Same set of labels is being applied to job on creation.
For DirectJobManager we just start with empty job list.

Refactoring:

1. JobServiceTest was replaced with JobServiceIT

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?:

API:
1. listIngestionJobs now returns IngestionJob with list of FeatureSetReference instead of list of FeatureSet

Properties (core):
feast:
  jobs:
    coordinator:
      # moved here from feast.jobs
      consolidate-jobs-per-source: false
      
      # labels that being applied to new jobs and used to filter existing jobs
      jobSelector:
        application: feast