MAINT: Add benchmarking files

[jhlegarreta]

Add benchmarking files so that nifreeze can be benchmarked using asv:

• Add the actual files that allow to benchmark different nifreeze capabilities.
• Add a new benchmark optional dependencies section to pyproject.toml.
• Add the asv configuration file.
• Add a README.rst file to explain how to run the benchmarking.
• Add a GitHub Actions workflow file to run the benchmarks for every PR.

[jhlegarreta]

Thought this would be relevant for when we will be needing to measure/benchmark nifreeze. This is a shy attempt to it. A few thoughts:

• Do we prefer/want a benchmark section to be added to tox.ini?
• Maybe a smaller testing/benchmarking dataset should be used. Especially taking into account that the GHA runners have very limited resources, and that I had to increase the default_benchmark_timeout value.
• This PR is by no means meant to be comprehensive; it is meant to be an initial step: further abstraction and sophistication so that we avoid boilerplate code, etc. (e.g. the scikit-learn way could serve as an inspiration) are left for a separate PR.
• The asv.conf.json file is placed at the benchmarks folder. Let me know if we want to move this to the project root.
• Eventually we will be willing to compare across different commits/over time so that we avoid introducing changes that are detrimental to performance.
• May need to pin dependencies, which will also require maintenance, since at some point we will want to measure the performance with modern, faster versions of packages.

An issue could be opened to keep track of the relevant comments above.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.85%. Comparing base (a78af6c) to head (ec78a80).
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #55      +/-   ##
==========================================
+ Coverage   65.74%   65.85%   +0.10%     
==========================================
  Files          19       19              
  Lines         943      943              
  Branches      121      121              
==========================================
+ Hits          620      621       +1     
+ Misses        278      277       -1     
  Partials       45       45              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[oesteban]

I'm not fully sure what's ASV about, but it looks useful :) Happy to see forward-looking initiatives @jhlegarreta.