refactor: modularize port monitoring and flatten local closures

[bhagathkrishnacdac]

Description
This PR refactors the port monitoring logic (_monitor_ports) to resolve cognitive complexity and flatten deeply nested closures. The helper functions, print generators, and rate calculations have been moved to module-level private functions.

Key Changes

• Decoupled Monitoring Loop: Extracted the core loop execution to _monitor_ports_loop to keep the primary CLI command interface flat.
• Isolated Calculations:
  • Moved the delta calculations and metric differential parsing to _calculate_port_delta.
  • Moved the stats aggregation logic to _aggregate_port_stats.
• Standardized Printing: Extracted formatting operations to _format_and_write_port_data and modernized CSV data compilation using Python comprehensions instead of maps with lambdas.
• Removed Variable Leakage dependency: Explicitly accessed the final port index in the header generator instead of relying on scoped variable leakage from the loops.