Add benchmark tests based on golden files

[dirkschumacher]

This adds a set of benchmark tests for all golden files. This allows us to quickly run some benchmarks that cover quite a bit of code. Of course that does not replace running longer on bigger instances, but it's a nice middle ground I hope.

to run them

go test -benchmem -run=^$ -count 10 -bench ^Benchmark ./... > old.txt
# make changes to code
go test -benchmem -run=^$ -count 10 -bench ^Benchmark ./... > new.txt 
benchstat old.txt new.txt

[merschformann]

Nice. I'd love to automate this. 🤔