[Feature Request] Standardized color awareness via the ${FORCE_COLOR} and ${NO_COLOR} environment variables

[leycec]

This feature request to my older self ^{...hi, older self! really hope you got your hair back somehow} is to remind myself that Python supports various environment variables to globally control color output across both the Python interpreter itself and third-party packages:

• ${NO_COLOR}, first introduced under Python 3.13 and taking precedence over ${FORCE_COLOR}.
• ${FORCE_COLOR}, first introduced under [we have no idea].
• ${PYTHON_COLOR}, which is unique to the Python interpreter itself and thus irrelevant for our purposes. Begone, foulest environment variable!

@beartype currently supports a @beartype-specific ${BEARTYPE_IS_COLOR} tri-state environment variable enabling end users to externally control colourization of @beartype output. That's great – but insufficient. Instead, @beartype should:

1. If ${BEARTYPE_IS_COLOR} is explicitly set, defer to that.
2. Else if ${NO_COLOR} is explicitly set, defer to that.
3. Else if ${FORCE_COLOR} is explicitly set, defer to that.

Beartype: I have a blistering headache already and it's only Tuesday. 🥴