Speed improvements for pack/unpack functions in protocol/types.py

[billyevans]

I noticed that pack/unpack functions from https://github.com/dpkp/kafka-python/blob/master/kafka/protocol/types.py might be slightly improved. I made pre-compilation for them. It gives about 10% better performance compared to the current implementation.
Consumption of 100msg:

239884    0.187    0.000    0.287    0.000 types.py:18(_unpack) # new version
239884    0.192    0.000    0.323    0.000 types.py:17(_unpack)

I also made some profiling for producers/consumers. It gives about 1-1.5% time savings.
My changes billyevans@99bf021

Should I make a PR?

[jeffwidman]

I am not super familiar with the struct interfaces, but at first glance, this looks like a straightforward change with an obvious performance win.

So yes, I'd appreciate a PR @billyevans

[tvoinarovskyi]

Seems nice to me

[jeffwidman]

I created the PR and cherry-picked the commit in #1619 so that we don't forget to add this.