increase() function for unwrapped values

[loganmc10]

Is your feature request related to a problem? Please describe.
I'm using Loki to gather Netflow data. The unwrapped value is a "Bytes" counter, which is always increasing. I need to calculate "top talkers" and get the total data transferred. Right now I'm doing last_over_time()-first_over_time(), which works, but it's a little slow since there are thousands of unique label sets/conversations.

Also, last_over_time()-first_over_time() won't properly deal with breaks in monotonicity like increase() would/should.

Describe the solution you'd like
Prometheus has an increase() function for counters. It would be nice to be able to use that, I assume it would be faster than last_over_time-first_over_time, since it isn't doing 2 different queries?

Describe alternatives you've considered
last_over_time()-first_over_time()

Additional context
This is what I'm doing currently to get the top 20 conversations (this is done in Grafana so there are some dashboard variables in use):

topk(20,sum by (SrcAddr,DstAddr,SamplerAddress, DstPort, Proto) (last_over_time({job="netflow",SamplerAddress=~`${sampler:regex}`} | json | SrcAddr=~".*${src_addr}.*" DstAddr=~".*${dst_addr}.*" | unwrap Bytes[$__range]) - first_over_time({job="netflow",SamplerAddress=~`${sampler:regex}`} | json | SrcAddr=~".*${src_addr}.*" DstAddr=~".*${dst_addr}.*" | unwrap Bytes[$__range])))