Added support for inspecting and de-identifying batched content

## Feature Feature Added support for inspecting and de-identifying batched content. You can now include a `[BatchContentItem](https://cloud.google.com/sensitive-data-protection/docs/reference/rest/v2/ContentItem#BatchContentItem)` in your `[ContentItem](https://cloud.google.com/sensitive-data-protection/docs/reference/rest/v2/ContentItem)` requests.