Export utils for import tracking and refs

[alexzielenski]

Avoids duplication of default tag parsing to be used in OpenAPI-gen

• Exports the function used by defaulter-gen to parse symbols for use with OpenAPI.
• Refactors the same function to take the source comment package path as input to avoid bugs with local symbols

Also includes some cleanup around the ImportTracker since OpenAPI-gen also needs to use AddSymbol:

• Adds NewImportTrackerForPackage so that local package can be provided to DefaultImportTracker
• Exposes AddSymbol on ImportTracker to be used by OpenAPI-gen and defaulter-gen
• Removes defaulter-gen's local symbolTracker interface since it is no longer necessary

required by kubernetes/kube-openapi#419

[alexzielenski]

/cc @apelisse

[apelisse]

I don't see a test being updated, shouldn't we have a test if this becomes a public method?

[alexzielenski]

added local package test

[apelisse]

Thanks
/lgtm

[sttts]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: alexzielenski, apelisse, sttts

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