Update skaffold init --analyze to handle more builder types

[TadCordle]

This is a follow-up to #2274.

Currently, skaffold init --analyze only shows dockerfiles and k8s images found, which isn't useful for non-dockerfile-based builder detection. This PR updates the schema to provide more useful information for IDEs to consume.

This PR:

• Renames the "dockerfiles" field to more general "builders" and changes it to be a list of structs containing a "name" and "payload" field rather than just a list of paths
  • "name" is the name of the builder that was detected, e.g. "Docker", "Jib", etc.
  • "payload" is the information parsed from the build configuration, which will vary depending on which builder was detected
• Changes "images" from a list of strings to a list of structs with a "name" and "promptForArtifactSource" field
  • "name" is the name of the image
  • "promptForArtifactSource" was added to allow IDEs to easily identify which builder/image pairs were automatically resolved (false) and which pairs will require prompting from the user (true) (with the addition of the Jib builder, some builder/image pairs will be automatically resolved).

Previous output:

{
    “dockerfiles”:[”/path/to/Dockerfile”, “another/Dockerfile”, ...],
    ”images”:[“gcr.io/project/image”, “another/image”, …],
}

Example new output:

{
    “builders”:[
        {
            “name”:“Docker”,
            “payload”:{“path”: “path/to/Dockerfile”},
        },
        {
            “name”:“Jib Gradle Plugin”,
            “payload”:{
                “path”:“path/to/build.gradle”,
                “configuredImage”:“gcr.io/project/image”,
                “project”:“child-project-name”
            },
        },
        ...
    ],
    “images”:[
        {“name”:”gcr.io/project/image”, “promptForArtifactSource”:”false”},
        {“name”:”another/image”, “promptForArtifactSource”:”true”},
    ]
}

[codecov]

Codecov Report

Merging #2327 into master will increase coverage by 4.36%.
The diff coverage is 66.66%.

Impacted Files	Coverage Δ
pkg/skaffold/docker/docker_init.go	93.33% <100%> (-0.22%)	⬇️
cmd/skaffold/app/cmd/init.go	56.52% <22.22%> (+1.52%)	⬆️
pkg/skaffold/initializer/init.go	43.98% <72.09%> (+5.15%)	⬆️
pkg/skaffold/docker/remote.go	35.41% <0%> (-13.16%)	⬇️
pkg/skaffold/docker/image.go	70.58% <0%> (-5.21%)	⬇️
pkg/skaffold/schema/v1beta9/upgrade.go	85.71% <0%> (-3.33%)	⬇️
cmd/skaffold/app/cmd/config.go	100% <0%> (ø)	⬆️
cmd/skaffold/app/cmd/commands.go	100% <0%> (ø)	⬆️
pkg/skaffold/kubernetes/context/context.go	100% <0%> (ø)	⬆️
pkg/skaffold/docker/image_util.go	0% <0%> (ø)	⬆️
... and 30 more

[loosebazooka]

@nkubala any chance you could look at this, given you familiarity with skaffold init?

[chanseokoh]

Looks good. I believe the VS code team is in sync with the schema change?

[TadCordle]

@chanseokoh Yeah, although there's one request to change Docker's payload to be in the form of {"path": "path/to/Dockerfile"} rather than just "path/to/Dockerfile", so I think I'll change that real quick.

[TadCordle]

@sujit-kamireddy Feel free to take a look and suggest changes as well.

[sujit-kamireddy]

Merging this will break the IDEs due to the new output format. Thanks @balopat for bringing this up. Please hold on merging this till we lock on the plan.

[dgageot]

LGTM with a few nits

[balopat]

We agreed on to put this behind a hidden feature flag to keep backward compatibility for now with the Cloud Code extensions.

[TadCordle]

@balopat done

[balopat]

one nit on the nit fixes then it's LGTM!