Move benchmarks outside pythran package

[stratakis]

The test_ prefix of the benchmark file was making
pytest collect it and use the benchmarks directory as
root, having the tests failing.

Rename the file so it's not collected via the usual
pytest runs.

[stratakis]

Discovered it while trying to update to the latest version in Fedora.

Since there was no an __init__.py file there, pytest was entering the benchmarks directory and using that as root. Placing the benchmarks outside the tests dir works without issues (although I didn't try to run the benchmark code, I assume codspeed should be utilized)

[stratakis]

It seems pytest might still be collecting this file, changing to draft for a bit till I properly test it.

[serge-sans-paille]

ack. Just so you know I removed codspeed integration recently, so don't worry too much about integration.

I do run benchmark tests locally through

PYTHONPATH=$PWD py.test pythran/benchmarks/test_benchmark.py -v

[stratakis]

Changing the name of the file so pytest doesn't collect it, hence it won't change directory seems to work. My initial assumptions of the lack of an init file was not correct, the file naming scheme was the culprit. Already tested in Fedora and tests run successfully.

[stratakis]

Seems that I'm not able to change the title of the PR, but the commit message should be relevant.