Centralize environment variables

All environment variables should be defined in a centralized location (checkov/common/util/env_vars_config.py) rather than scattered throughout the codebase. This approach enhances maintainability, promotes consistency, and simplifies tracking of configuration settings.

When adding a new environment variable:

1. Define it in the centralized config file with proper type conversion
2. Add a descriptive comment explaining its purpose
3. Import and use the variable in your code instead of direct os.getenv() calls

Always use strtobool() for boolean environment variables since bool('False') evaluates to True.

Example:

# In checkov/common/util/env_vars_config.py
from distutils.util import strtobool

# Controls whether to ignore hidden directories (default: True)
IGNORE_HIDDEN_DIRECTORY_ENV = strtobool(os.getenv("CKV_IGNORE_HIDDEN_DIRECTORIES", "True"))

# In your code
from checkov.common.util.env_vars_config import IGNORE_HIDDEN_DIRECTORY_ENV

if IGNORE_HIDDEN_DIRECTORY_ENV:
    # Skip hidden directories logic here