Major refactor of config classes a and config include logic

[nat-n]

BREAKING CHANGE: included config now loads envfiles relative to the cwd specified on the include option (if any).

New/updated special env vars:

• POE_CONF_DIR: the path to the dir containing the config file that defines the running task or the cwd set when including the config
• POE_DEBUG makes poe print more stuff to help with debugging

Refactor specifics:

• Introduce PoeOptions class for deserializing config. I would have used pydantic but it's too heavy for use in a CLI tool like this.
• Keep config from different files separate within PoeConfig
• Collect config validation logic in the config classes and declare config types in more detail
• Make error reporting more structured and consistent

Also:

• Fixed bug that caused some task validation to be skipped for tasks with args
• Improve consistency and coverage for config validation
• Fix crash in switch with args naked string for control
• PoeConfig.load will load everything again if called a second time
• remove pylint from the project
• Enable ANSI color output by default inside GitHub Actions