Conformance tests for Training operator

[johnugeorge]

Add Kubeflow conformance tests for training operator components

Ref: kubeflow/kubeflow#6485

/cc @james-jwu

[johnugeorge]

Design: https://docs.google.com/document/d/1TRUKUY1zCCMdgF-nJ7QtzRwifsoQop0V8UnRo-GWlpI/edit#

[nagar-ajay]

I'll start working on this.

[johnugeorge]

Container implementation added in #1780

[johnugeorge]

Closing this PR as conformance changes are merged