Log field/filtering improvements

This is a combined new feature for the following log data improvements:

• Adding log fields for cache response code, header length and content length (to mirror the fields that already exist for the server and client)
• Adding a log field container for the cached response headers (to mirror the field container that already exists for the server and client headers)
• Adding the ability to filter custom logs based on field container members
• Tweaking where we calculate the logged response body length(s) so that it accurately reflects abnormal termination cases like client/server aborts or transforms such as the range transform (when pertaining to cached responses)