feat(parallel-tests): update Makefile to perform tests in parallel

[glevco]

I noticed that running our tests take a long time, usually more than 1 hour in our CI though GitHub Actions. I tried this simple pytest plugin, pytest-xdist, which parallelizes test runs in multiple CPU cores. It's the main recommended plugin for that purpose, and has more than 1.1k starts on GitHub.

It's hard to get exact statistics on job execution times for a precise benchmark, but from taking a look at previous PRs and comparing with runs on #532, the difference is noticeable. When running locally, on computers with more cores than the GitHub Actions runners, the time gains are even larger.

Acceptance criteria:

• Install the pytest-xdist plugin
• Update Makefile commands to parallelize tests

[msbrogli]

What was the performance gain in your computer?

[jansegre]

I just noticed that the codecov wasn't updated (it needs the pytest plugin to run correctly). Maybe it's a one off error, can you check that it wasn't affected and that the codecov still updates correctly?

[codecov]

Codecov Report

Merging #533 (c3704b7) into dev (42bfc1c) will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##              dev     #533      +/-   ##
==========================================
+ Coverage   83.11%   83.14%   +0.02%     
==========================================
  Files         209      209              
  Lines       18512    18512              
  Branches     2587     2587              
==========================================
+ Hits        15386    15391       +5     
+ Misses       2560     2557       -3     
+ Partials      566      564       -2     

Impacted Files	Coverage Δ
hathor/transaction/storage/transaction_storage.py	89.97% <0.00%> (ø)
hathor/p2p/node_sync.py	84.95% <0.00%> (+0.48%)	⬆️
hathor/p2p/manager.py	68.22% <0.00%> (+1.00%)	⬆️

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[glevco]

What was the performance gain in your computer?

@msbrogli I ran make tests-lib on my computer (a Quad-Core Intel Core i7 MacBook Pro). In the dev branch, it takes 55minutes:

In this branch, it takes 18 minutes:

[glevco]

I just noticed that the codecov wasn't updated (it needs the pytest plugin to run correctly). Maybe it's a one off error, can you check that it wasn't affected and that the codecov still updates correctly?

@jansegre it was probably a one off, it has been updated now

[msbrogli]

What was the performance gain in your computer?

@msbrogli I ran make tests-lib on my computer (a Quad-Core Intel Core i7 MacBook Pro). In the dev branch, it takes 55minutes:

In this branch, it takes 18 minutes:

Thanks for the benchmark.