revsetbenchmark: fix semicolon
revsetbenchmark: convert update to proper subprocess call
revsetbenchmark: convert performance call to proper subprocess call
revsetbenchmark: convert revision display to proper subprocesscall
revsetbenchmark: get revision to benchmark in a function

And move it to proper subprocess call.

--HG--
extra : amend_source : e7f38a1e2687b6ca59e32c419d161ba38caafabb
revsetbenchmark: retrieve the benchmark value in python

We retrieve the output of the perf extension and print it ourself. This open the
door to processing of this data in the script.
revsetbenchmark: add a summary at the end of execution

The summary list timing per revset making it much more easier to compare
revision to each other.