skaffold deploy to support -t for tags

[matti]

skaffold.yaml:

apiVersion: skaffold/v2alpha2
kind: Config
build:
  artifacts:
    - image: first
      context: components/first
    - image: second
      context: components/second
deploy:
  kustomize:
    path: kustomize

If I have already built the images I need to provide --image for every artifact:

skaffold deploy \
  -d my.registry.example.com \
  --images "first:mytag" \
  --images "second:mytag"

So if skaffold deploy supported -t like other commands, then this would become just:

skaffold deploy \
  -d my.registry.example.com \
  -t mytag

and the skaffold deploy ... command wouldn't need to know the artifacts.

[matti]

Somewhat related to #922

[gsquared94]

This seems like a reasonable ask. However there seem to already be a few different ways of passing info from build to deploy. We'll probably need to be a bit more consistent.

[tejal29]

We decided to add this feature. Removing the discuss label