Use go-containerregistry to push and pull

[imjasonh]

Using this library should make it easier to integrate with Tekton controller components when the time comes.

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[pierretasci]

Just nitpicks.

Also, I tried to check this out and run it locally on a simple pipeline. It hung for a long time and didn't give much indication what it was doing. Might be worth looking into a way to print out what is going on.

[imjasonh]

Also, I tried to check this out and run it locally on a simple pipeline. It hung for a long time and didn't give much indication what it was doing. Might be worth looking into a way to print out what is going on.

Hmm, I'm not sure what would cause this to hang, since it's basically just a bunch of small HTTP requests and tar operations. Maybe auth is the culprit?

google/go-containerregistry#670 tracks upload/download progress repoprting in go-containerregistry, but I'm not sure there's much movement yet.

[imjasonh]

/test tekton-experimental-unit-tests

[pierretasci]

LGTM!

[sthaha]

/lgtm
/approve

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