A metrics collector for Kubeflow Pipeline Metrics artifacts

/kind feature

**Describe the solution you'd like**
Currently a aim is to do parameter tuning over pipelines in katib (#1914, #1993).

Kubeflow pipelines allow for dedicated metrics artifacts:
https://kubeflow-pipelines.readthedocs.io/en/master/source/dsl.html?h=metrics#kfp.dsl.Metrics
https://www.kubeflow.org/docs/components/pipelines/v1/sdk/pipelines-metrics/

Having a dedicated[ Katib sidecar metrics collector](https://www.kubeflow.org/docs/components/katib/experiment/#metrics-collector) that collects the metrics from this artifacts, would make pipelines and katib work together quite nicely.

The current workaround is to use the stdout collector, but this causes issues with the complex commands in pipeline components (#1914, will add dedicated issue soon).

**Anything else you would like to add:**
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Read the linked Kubeflow Pipelines Metrics and Katib metrics collector documentation first, then locate the existing Katib sidecar collector entry point. Determine how the collector should consume pipeline Metrics artifacts; done means Katib can use those artifacts for pipeline parameter tuning.

Written by the indexing model from the issue text.