[API] Move KubeObject to api module

[mozesl-nokia]

This PR moves the KubeObject, kptfileko and other related types and parsing methods into the kpt api module from the SDK. With this move, we can break the dependency between the main kpt module and the SDK.

This means the following import changes will be necessary (only for the moved types):

• github.com/kptdev/krm-functions-sdk/go/fn -> github.com/kptdev/kpt/api/kubeobject
• github.com/kptdev/krm-functions-sdk/go/fn/kptfileko -> github.com/kptdev/kpt/api/kubeobject/kptfile

I've reorganised quite a bit of the files so that they are not as large as before, as well as fixing linting issues.

The fnresultv1.ResultItem type was parctically duplicated (once again) amongs the KubeObject types, this was deduplicated, meaning a breaking API change for the consumers of the SDK types. It should not affect yaml/json, only the go types.

There is this comment on ResourceList:

// ResourceList is a Kubernetes list type used as the primary data interchange format
// in the Configuration Functions Specification:
// https://github.com/kubernetes-sigs/kustomize/blob/master/cmd/config/docs/api-conventions/functions-spec.md
// This framework facilitates building functions that receive and emit ResourceLists,
// as required by the specification.

and I am fairly certain the deduplication did not break this, but we may want to check (if we still care about this, the comment is from 2022).

For reviewers: As this is a massive change wholesale, I suggest looking at the changes commit-by-commit to see what has actually changed besides just copy-pasting.

AI disclosure:

• Cursor's Composer 2.5 and Grok 4.7 were used mainly for analysis and menial tasks, such as rewriting imports.

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[liamfallon]

Looks good, thanks @mozesl-nokia

[efiacor]

I think we should add the api/kubeobject dir to the sonar.sources
https://github.com/kptdev/kpt/blob/main/sonar.properties#L10
I know it creates an onus on you to create some coverage for the node module but if it's going public then we prob need it.

[sonarqubecloud]

Quality Gate failed

Failed conditions
30.4% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud