PR: Implement Support to Load Environment Variables from File

[KelSolaar]

Summary

This PR implements support to load environment variables from a file.

It is now possible to create a ~/.colour-science/colour-science.jenv JSON file from which Colour will load environment variables from:

{
  "COLOUR_SCIENCE__COLOUR__SHOW_WARNINGS_WITH_TRACEBACK": 1
}

The following new environment variables are now supported:

• COLOUR_SCIENCE__FILTER_RUNTIME_WARNINGS: Filter Colour runtime warnings.
• COLOUR_SCIENCE__FILTER_USAGE_WARNINGS: Filter Colour usage warnings.
• COLOUR_SCIENCE__FILTER_COLOUR_WARNINGS: Filter Colour warnings, this also filters Colour usage and runtime warnings.
• COLOUR_SCIENCE__FILTER_PYTHON_WARNINGS: Filter Python warnings.

This should help with #1221 and #1237.

Preflight

Code Style and Quality

• Unit tests have been implemented and passed.
• Pyright static checking has been run and passed.
• Pre-commit hooks have been run and passed.
• [N/A] New transformations have been added to the Automatic Colour Conversion Graph.
• [N/A] New transformations have been exported to the relevant namespaces, e.g. colour, colour.models.

Documentation

• New features are documented along with examples if relevant.
• The documentation is Sphinx and numpydoc compliant.

[coveralls]

coverage: 99.721% (-0.009%) from 99.73%
when pulling 2baa1a9 on feature/jenv
into 8098fbc on develop.