refactor: move hathor settings to yaml configuration files [part 1/2]

[glevco]

Acceptance Criteria

• Install pyyaml dependency (the go to, canonical yaml implementation for python, repo)
• Add utility methods to HathorSettings named tuple to create it from a dict or a yaml file, leveraging pydantic for validation
• Create yaml files to substitute python config files for all network settings (mainnet, testnet, and unitttests).
  • The python configuration files are removed in a separate PR: refactor: move hathor settings to yaml configuration files [part 2/2] #597
• Update get_settings.HathorSettings() to get settings from yaml files instead of python modules.
  • First, it tries to get a python module settings, and logs a deprecation warning if it's found. Then, it gets the yaml
  • This change should be backwards compatible with our current code. A breaking change removing support for settings via python modules will be introduced in a future release.
• Implement tests to make sure the yaml versions of settings are equal to their python versions, during the migration.

[codecov]

Codecov Report

Merging #593 (83e1391) into master (3b372ac) will decrease coverage by 0.03%.
The diff coverage is 77.77%.

@@            Coverage Diff             @@
##           master     #593      +/-   ##
==========================================
- Coverage   83.68%   83.65%   -0.03%     
==========================================
  Files         231      232       +1     
  Lines       19622    19675      +53     
  Branches     2687     2695       +8     
==========================================
+ Hits        16421    16460      +39     
- Misses       2608     2619      +11     
- Partials      593      596       +3     

Impacted Files	Coverage Δ
hathor/conf/get_settings.py	55.00% <56.52%> (-27.61%)	⬇️
hathor/conf/settings.py	97.08% <84.61%> (-2.92%)	⬇️
hathor/builder/cli_builder.py	71.82% <100.00%> (+0.15%)	⬆️
hathor/conf/__init__.py	100.00% <100.00%> (ø)
hathor/utils/pydantic.py	100.00% <100.00%> (ø)
hathor/utils/yaml.py	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

[glevco]

Based on @msbrogli's comments, I decided to keep HathorSettings as a NamedTuple and just leverage pydantic's validation to instantiate it from a yaml file, instead of actually changing HathorSettings to pydantic.BaseModel. Done in 10ac376

[glevco]

@jansegre

I like the proposed new format. But for the sake of minimizing migration issues, I would rather have this PR still try to load a settings module using the old format and emit a deprecation warning.

Makes sense, done in e0c35ad. I used HATHOR_CONFIG_YAML as you suggested, and also added an equivalent CLI option for it. I have updated the Acceptance Criteria accordingly.

Another point is that most of the time I customize the settings locally, and also when we customize it for our deploys, we inherit a specific config (mainnet/testnet) and alter only a few properties. This is particularly convenient for when there are new parameters, such that the customized settings don't need any change. I think we should consider supporting some settings inherit mechanism before deprecating the old settings (it doesn't have to be on this PR).

I created an issue for that in #614. I left it in the To Do column of our project I'll do it as soon as I close some of the current tasks.