Changes to POST /api/v1beta/token_usage/estimate

added the optional property file_details/items/coverage to the response with the 200 status

added the optional property file_details/items/full_token_count to the response with the 200 status

added the optional property file_details/items/included_token_count to the response with the 200 status

added the optional property file_details/items/inclusion_mode to the response with the 200 status

added the optional property file_details/items/reason to the response with the 200 status