Azure container registry (aka ACR) support

[Shaked]

Is your feature request related to a problem? Please describe.

I have been testing Makisu using GCR and it works great.

As I'm also working with Azure's registry aka ACR, I'd like to push and use Makisu's cache together with ACR.

Describe the solution you'd like

Please support https://github.com/Azure/acr-docker-credential-helper same as you do with GCR and ECR

Describe alternatives you've considered

I assume I'd have to continue using Kaniko for now when it comes to ACR as I must have a proper solution for that.