add handling of empty versioning and cors in hand written storage bucket

[daniel-cit]

This PR solves the issue Validator crashes when validating storage resource when versioning is not yet defined in terraform-validator

Release Note Template for Downstream PRs (will be copied)

Fix handling of empty versioning and cors in hand written storage bucket for terraform-google-conversion

[modular-magician]

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[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

TF Conversion: Diff ( 1 file changed, 4 insertions(+), 1 deletion(-))

[modular-magician]

I have triggered VCR tests based on this PR's diffs. See the results here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=178049"