helper/resource: Prevent Inconsistent dependency lock file errors when using ExternalProviders outside the hashicorp namespace

[bflad]

Reference: https://discuss.hashicorp.com/t/acceptance-testing-sdk-framework-upgrade-issue/44166
Reference: https://www.terraform.io/plugin/framework/migrating/testing

By default, Terraform CLI will use the registry.terraform.io hostname and hashicorp namespace for provider addresses if there is not a terraform configuration block with an explicit configuration. Previously, the testing framework would automatically generate a temporary configuration with the terraform configuration block for running terraform init, but it did not include this extra configuration along with a given TestStep Config. When working with hashicorp namespace providers, this isn't an issue because of the Terraform CLI defaults.

External provider developers could manually workaround this issue by including the terraform configuration block as part of their TestStep Config, however this is certainly confusing and error prone.

This issue is especially pertinent now as the sdk/v2 to framework migration guide shows acceptance testing which uses ExternalProviders extensively for proving successful migrations without plan differences.

Previously before code adjustments:

=== CONT  TestTest_TestCase_ExternalProviders_NonHashiCorpNamespace
    testcase_providers_test.go:236: Step 1/1 error: Error running pre-apply refresh:
        Error: Inconsistent dependency lock file

        The following dependency selections recorded in the lock file are
        inconsistent with the current configuration:
          - provider registry.terraform.io/hashicorp/scaffoldingtest: required by this configuration but no version is selected

        To update the locked dependency selections to match a changed configuration,
        run:
          terraform init -upgrade
--- FAIL: TestTest_TestCase_ExternalProviders_NonHashiCorpNamespace (1.91s)

=== CONT  TestTest_TestCase_ExternalProvidersAndProviderFactories_NonHashiCorpNamespace
    testcase_providers_test.go:258: Step 1/1 error: Error running pre-apply refresh:
        Error: Inconsistent dependency lock file

        The following dependency selections recorded in the lock file are
        inconsistent with the current configuration:
          - provider registry.terraform.io/hashicorp/scaffoldingtest: required by this configuration but no version is selected

        To update the locked dependency selections to match a changed configuration,
        run:
          terraform init -upgrade
--- FAIL: TestTest_TestCase_ExternalProvidersAndProviderFactories_NonHashiCorpNamespace (0.46s)

=== CONT  TestTest_TestStep_ExternalProviders_NonHashiCorpNamespace
    teststep_providers_test.go:304: Step 1/1 error: Error running pre-apply refresh:
        Error: Inconsistent dependency lock file

        The following dependency selections recorded in the lock file are
        inconsistent with the current configuration:
          - provider registry.terraform.io/hashicorp/scaffoldingtest: required by this configuration but no version is selected

        To update the locked dependency selections to match a changed configuration,
        run:
          terraform init -upgrade
--- FAIL: TestTest_TestStep_ExternalProviders_NonHashiCorpNamespace (0.32s)

=== CONT  TestTest_TestStep_ExternalProvidersAndProviderFactories_NonHashiCorpNamespace
    teststep_providers_test.go:325: Step 1/1 error: Error running pre-apply refresh:
        Error: Inconsistent dependency lock file

        The following dependency selections recorded in the lock file are
        inconsistent with the current configuration:
          - provider registry.terraform.io/hashicorp/scaffoldingtest: required by this configuration but no version is selected

        To update the locked dependency selections to match a changed configuration,
        run:
          terraform init -upgrade
--- FAIL: TestTest_TestStep_ExternalProvidersAndProviderFactories_NonHashiCorpNamespace (0.35s)

[bendbennett]

Nice. LGTM

[github-actions]

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