refactor: modularize traffic class monitoring and simplify loop closures

[bhagathkrishnacdac]

Description
This PR refactors _monitor_tcs to resolve cognitive complexity and flatten deeply nested closures. The helper functions, print generators, and rate calculations used to report traffic class (TC) runtime metrics have been moved to module-level private functions.

Key Changes

• Decoupled Monitoring Loop: Extracted the core loop execution to _monitor_tc_loop to keep the primary CLI command interface clean.
• Isolated Rate Calculations:
  • Moved the delta calculations and metric differential parsing to _calculate_tc_delta.
  • Moved TC scheduling ratio calculations (packets-per-batch and cycles-per-packet ratios) to _format_tc_data.
• Standardized Terminal Layouts: Replaced nested print format generators with simplified, flat templates and modernized CSV output generation using list comprehensions instead of maps with lambdas.
• Fixed Variable Scope Reliance: Correctly accessed the final TC index in the header generator instead of relying on scoped variable leakage from the loops.