Fix perma diff problem during TF import

[modular-magician]

fixes #13515
TLDR: Resource groups has a field initialGroupConfig and the default value is "EMPTY". During a TF import, this field is not set to "EMPTY" if it has no value.

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• Ensured that all new fields I added that can be set by a user appear in at least one example (for generated resources) or third_party test (for handwritten resources or update tests).
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Release Note Template for Downstream PRs (will be copied)

cloudidentity: fixed an issue on `initialGroupConfig` field when users make an import.

Derived from GoogleCloudPlatform/magic-modules#7348

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