Performance tests

We already have a couple of somewhat niche performance tests in cmd/benchmark. However, it'd be great to have more representative performance tests that lie between microbenchmarks on one end and real execution of all main net blocks on the other. Something like executing a bunch (1000?) of some test blocks using MDBX. Ideally those test blocks should capture performance-salient features of recent main net blocks.

Such performance tests could be used, among other things, to prevent performance regressions.