Enable usage logs to track the downloads for artifacts in knative-releases project #3231
Description
Currently, the network egress cost for knative-releases project is ~$1k per month, and it's because this project hosts all the Knative release artifacts in GCS and GCR, and all the Knative users will download them from it.
As there are more and more Knative users, the cost for it will keep growing. To get a better understanding on where the costs come from and also for potential future improvements, it'll better track the usage for the Knative releases. Usage logs is the recommended solution to do this - https://cloud.google.com/storage/docs/access-logs
/cc @upodroid