feat(onboarding): Add validation support for GCP CDR onboarding (#490)

* feat(onboarding): Add validation support for GCP CDR onboarding

Change summary:
-----------------
1. Support for GCP CDR validation during onboarding using WIF. Mainly fixed
   the case for metadata population when WIF is passed.
2. Added GCP CDR tests
3. Modified the structure and organization of acceptance test suite for
   sysdig_secure_cloud_auth_account resource.

Testing done:
---------------
Validated the acceptance tests against staging.

* Remove unnecessary log

* Update acc test

* Fix comment

Author: ravinadhruve10

sysdig/resource_sysdig_secure_cloud_auth_account.go

@@ -387,25 +387,26 @@ func constructAccountComponents(data *schema.ResourceData) []*cloudauth.AccountC
 					if data.Get(SchemaCloudProviderType).(string) == cloudauth.Provider_PROVIDER_GCP.String() {
 						spGcp := &internalServicePrincipalMetadata{}
 						err = json.Unmarshal([]byte(value.(string)), spGcp)
+						// special handling if GCP service principal key is present, decode and unmarshal it before populating all the metadata
+						var spGcpKey *cloudauth.ServicePrincipalMetadata_GCP_Key
 						if len(spGcp.Gcp.Key) > 0 {
 							var spGcpKeyBytes []byte
 							spGcpKeyBytes, err = base64.StdEncoding.DecodeString(spGcp.Gcp.Key)
 							if err != nil {
 								diag.FromErr(err)
 							}
-							spGcpKey := &cloudauth.ServicePrincipalMetadata_GCP_Key{}
-							err = json.Unmarshal(spGcpKeyBytes, spGcpKey)
-							component.Metadata = &cloudauth.AccountComponent_ServicePrincipalMetadata{
-								ServicePrincipalMetadata: &cloudauth.ServicePrincipalMetadata{
-									Provider: &cloudauth.ServicePrincipalMetadata_Gcp{
-										Gcp: &cloudauth.ServicePrincipalMetadata_GCP{
-											Key:                        spGcpKey,
-											WorkloadIdentityFederation: spGcp.Gcp.WorkloadIdentityFederation,
-											Email:                      spGcp.Gcp.Email,
-										},
+							err = json.Unmarshal(spGcpKeyBytes, &spGcpKey)
+						}
+						component.Metadata = &cloudauth.AccountComponent_ServicePrincipalMetadata{
+							ServicePrincipalMetadata: &cloudauth.ServicePrincipalMetadata{
+								Provider: &cloudauth.ServicePrincipalMetadata_Gcp{
+									Gcp: &cloudauth.ServicePrincipalMetadata_GCP{
+										Key:                        spGcpKey,
+										WorkloadIdentityFederation: spGcp.Gcp.WorkloadIdentityFederation,
+										Email:                      spGcp.Gcp.Email,
 									},
 								},
-							}
+							},
 						}
 					}
 				case SchemaWebhookDatasourceMetadata: