VPC Service Controls feature: Support to programmatically retrieve the list of services that are supported by VPC Service Controls is generally available

## Feature **VPC Service Controls feature:** Support to programmatically [retrieve the list of services](https://cloud.google.com/vpc-service-controls/docs/supported-products#list-services) that are supported by VPC Service Controls is [generally available](https://cloud.google.com/products#product-launch-stages). Using this feature, you also can [retrieve the list of methods and permissions](https://cloud.google.com/vpc-service-controls/docs/supported-products#list-methods) supported by VPC Service Controls for a service. * The following changes are made in the output of the `gcloud access-context-manager supported-services list` command: * The field name `SUPPORT_STAGE` is changed into `SERVICE_SUPPORT_STAGE`. * The status `BETA` is changed into `PREVIEW` in the `SERVICE_SUPPORT_STAGE` field. * A new status `DEPRECATED` is added in the `SERVICE_SUPPORT_STAGE` field. * The field name `supportStage` is changed into `serviceSupportStage` in the output of the `gcloud access-context-manager supported-services describe` command.