Introduce SimpleBaseSampler and remove load settings propagation

[y0z]

Motivation

We've decided to move SimpleBaseSampler from optunahub-registry to optunahub.samplers and remove settings propagation. This PR introduces SimpleBaseSampler and removes things that are no longer needed.

Description of the changes

• Add optunahub.samplers.SimpleBaseSampler
• Add docs for optunahub.samplers.SimpleBaseSampler
• Remove code for settings propagation from load_module and load_local_module
• Remove tests for settings propagation

[codecov]

Codecov Report

Attention: Patch coverage is 88.37209% with 5 lines in your changes missing coverage. Please review.

Project coverage is 81.95%. Comparing base (5cc1871) to head (59fedf3).
Report is 17 commits behind head on main.

Files	Patch %	Lines
optunahub/samplers/_simple_base.py	87.17%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #55      +/-   ##
==========================================
+ Coverage   81.90%   81.95%   +0.05%     
==========================================
  Files           4        6       +2     
  Lines         105      133      +28     
==========================================
+ Hits           86      109      +23     
- Misses         19       24       +5     

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[toshihikoyanase]

Thank you for your PR. The change looks good to me.

I confirmed that optunahub.samplers.SimpleBaseSampler actually worked with the whale optimization.

Since this PR includes some breaking changes, it might be kind to cover the changes regarding propagation in the PR title.

[toshihikoyanase]

[Note] This implementation is a copy of https://github.com/optuna/optunahub-registry/blob/main/package/samplers/simple/__init__.py, except for this docstring.