Create report analyzing image size trends

[lbussell]

With #745, image sizes are now ingested into our Kusto database. We should create a PowerBI report to analyze trends in image sizes.

I have created some basic documentation on using Kusto queries to analyze image sizes in our internal wiki. It includes a very simple example query to get the size of all images in a repo: https://dev.azure.com/dnceng/internal/_wiki/wikis/Acquisition%20and%20Deployment%20Team/1343/Image-Sizes