Standardize code & add checks and tests

[tddough98]

Makes a handful of improvements to the codebase to make contributions easier including

• add autoformatting with black
• add linting with ruff
• enforce formatting and linting locally with pre-commit hooks
• enforce formatting and linting for pull requests with a GitHub Action
• change variable and function naming to be consistent with PEP 8 style, mostly replacing PascalCase or UPPERCASE with snake_case
• refactor ENVIOutputLayer to make comm_disp and const_disp behavior more clear
• add tests for output_layers.py and utils.py
• add GitHub Action to run tests
• add .gitignore for Python codebase