Enable explainers to work with ModelMesh

[chinhuang007]

/kind feature

Describe the solution you'd like I would like the existing KServe explainers to work with Modelmesh.

Anything else you would like to add: The explainers currently work with predictors deployed by KServe, not the ones deployed by ModelMesh.

[chinhuang007]

High level analysis and proposal for explainability with ModelMesh can be found here.