Ad marketing_method-dimension from Merchant Center API#1977

Please add the marketing_method dimension to the Google Merchant Center connector.

Google Merchant API exposes marketing_method in ProductPerformanceView, with values such as ORGANIC and ADS.

We need it to segment product_clicks, product_impressions and product_ctr by Free Listings vs Shopping Ads, on product level. marketing_method is in the API, but not picked up by Windsor.

Main use case: reporting Free Listings and Ad clicks per product in Looker Studio.