Adding HIT / MISS as part of the logging

[hveiga]

Feature Overview

It would be great if we could get a hit or miss in each log to understand how effective the caching is. I believe we would need to modify the lines in here:

https://github.com/nginx/nginx-s3-gateway/blob/main/common/etc/nginx/nginx.conf#L56-L58

Do we think this is a helpful feature?

Also, we could do it conditionally and only enable if through an env var.

Alternatives Considered

No response

Additional Context

No response