feat(logging): update logging configuration and format

Refactor configure_logging to incorporate conditional handlers. Add color support in console output and toggle between console and JSON formatting based on the CONSOLE_LOGGING environment variable.

• Enable toggling between console and JSON formatters based on CONSOLE_LOGGING.
• Add color support to console logging when CONSOLE_LOGGING is enabled.
• Simplify processor list in structlog.configure.
• Set disable_existing_loggers.
• Update README.md to describe LOG_LEVEL and CONSOLE_LOGGING usage.

A part of: https://gitlab.developers.cam.ac.uk/uis/devops/iam/authentication/infrastructure/-/issues/168