Fix permadiff of encryption_configuration in resource_bigquery_table when API returns an empty object

[modular-magician]

Sometimes the API returns a table with "encryptionConfiguration": {} when the input omits this field.

Without this change, the Terraform state file would end up with

"encryption_configuration": [
  {
    "kms_key_name": "",
     "kms_key_version": ""
  }
]

This would cause the subsequent plan to end up with a diff of - encryption_configuration {} # forces replacement.

With this change, the new Terraform state file would have:

"encryption_configuration": []

This would no longer result in a permadiff.

Release Note Template for Downstream PRs (will be copied)

bigquery: Fix permadiff of encryption_configuration in resource_bigquery_table when API returns an empty object

Derived from GoogleCloudPlatform/magic-modules#9757

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