Add I/O read per second, fix bug sizing of io overview

[navidpadid]

This pull request extends the process overview functionality to support and display read byte rates (RD/s) alongside existing metrics, and updates the codebase to handle size fields with units (e.g., "1 GB", "100 MB") for I/O statistics. It also adds comprehensive test coverage for these new features.

Feature enhancements

• Added support for parsing and displaying read_bytes statistics with unit suffixes (B, KB, MB, GB, TB), similar to write_bytes, in the process overview plots. This includes a new RD/s sparkline and label in the UI.

Parsing improvements

• Introduced the parse_size_field_bytes function to robustly handle size fields with units when parsing I/O statistics. This ensures correct interpretation of values such as "1 GB" or "512 MB".

Testing updates

• Updated and expanded tests to cover new parsing logic and ensure the overview output includes the new RD/s metric, as well as correct handling and display of unit-suffixed values.