Add DSFs to references in snapshot tests (and other MM-generated tests)

[rileykarson]

This makes resources that are compliant with hashicorp/terraform-provider-google#4328 pass the import step.

If this PR is for Terraform, I acknowledge that I have:

• Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
• Generated Terraform, and ran make test and make lint to ensure it passes unit and linter tests.
• 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).
• Ran relevant acceptance tests (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).
• Read the Release Notes Guide before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 38 files changed, 281 insertions(+), 213 deletions(-))
Terraform Beta: Diff ( 39 files changed, 285 insertions(+), 216 deletions(-))

[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=143074"

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccDataSourceGoogleCloudFunctionsFunction_basic|TestAccDataSourceComputeBackendBucket_basic|TestAccCloudFunctionsCloudFunctionIamBindingGenerated|TestAccCloudFunctionsCloudFunctionIamMemberGenerated|TestAccCloudFunctionsCloudFunctionIamPolicyGenerated|TestAccIapAppEngineVersionIamBindingGenerated|TestAccIapAppEngineVersionIamMemberGenerated|TestAccIapAppEngineVersionIamBindingGenerated_withCondition|TestAccIapAppEngineVersionIamMemberGenerated_withCondition|TestAccIapAppEngineVersionIamPolicyGenerated|TestAccIapAppEngineVersionIamPolicyGenerated_withCondition|TestAccIapAppEngineServiceIamBindingGenerated|TestAccIapAppEngineServiceIamMemberGenerated|TestAccIapAppEngineServiceIamBindingGenerated_withCondition|TestAccIapAppEngineServiceIamPolicyGenerated|TestAccIapAppEngineServiceIamMemberGenerated_withCondition|TestAccIapAppEngineServiceIamPolicyGenerated_withCondition|TestAccAppEngineApplicationUrlDispatchRules_appEngineApplicationUrlDispatchRulesBasicExample|TestAccAppEngineServiceSplitTraffic_appEngineServiceSplitTrafficExample|TestAccAppEngineStandardAppVersion_appEngineStandardAppVersionExample|TestAccBigQueryJob_bigqueryJobExtractExample|TestAccBigQueryJob_bigqueryJobExtractTableReferenceExample|TestAccAppEngineStandardAppVersion_update|TestAccAppEngineFlexibleAppVersion_appEngineFlexibleAppVersionExample|TestAccAppEngineFlexibleAppVersion_update|TestAccBigQueryTable_HivePartitioning|TestAccBigQueryTable_HivePartitioningCustomSchema|TestAccBigQueryExternalDataTable_CSV|TestAccCloudFunctionsFunction_basic|TestAccCloudFunctionsFunction_update|TestAccCloudFunctionsFunction_firestore|TestAccCloudFunctionsFunction_pubsub|TestAccCloudFunctionsFunction_bucket|TestAccCloudFunctionsFunction_serviceAccountEmail|TestAccCloudFunctionsFunction_vpcConnector|TestAccComputeBackendBucket_backendBucketBasicExample|TestAccComputeBackendBucket_basicModified|TestAccComputeBackendBucket_withCdnPolicy|TestAccComputeBackendBucketSignedUrlKey_basic|TestAccComputeDisk_VSSWindows|TestAccComputeRegionNetworkEndpointGroup_regionNetworkEndpointGroupFunctionsExample|TestAccComputeRegionNetworkEndpointGroup_regionNetworkEndpointGroupAppengineExample|TestAccComputeUrlMap_urlMapBasicExample|TestAccDataprocCluster_withStagingBucket|TestAccDataprocCluster_withInitAction|TestAccDataprocCluster_withKerberos|TestAccFirebaseWebApp_firebaseWebAppBasicExample|TestAccLoggingBillingAccountSink_basic|TestAccLoggingBillingAccountSink_update|TestAccLoggingBillingAccountSink_heredoc|TestAccLoggingFolderSink_basic|TestAccLoggingFolderSink_removeOptionals|TestAccLoggingFolderSink_folderAcceptsFullFolderPath|TestAccLoggingFolderSink_update|TestAccLoggingFolderSink_heredoc|TestAccLoggingOrganizationSink_basic|TestAccLoggingOrganizationSink_update|TestAccLoggingOrganizationSink_heredoc|TestAccLoggingProjectSink_basic|TestAccLoggingProjectSink_updatePreservesUniqueWriter|TestAccLoggingProjectSink_heredoc|TestAccComputeResourceUsageExportBucket You can view the result here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=143081"