[fix] Remove custom classes

[vpchung]

Fixes #24

Changelog

• Remove custom classes and convert existing methods into functions that extend the synapseclient
• Remove support for python 3.9 (due to end-of-life in Oct 2025)
• Add unit tests
• General linting and release notes updates

Preview

Outwardly, everything still works the same

Before

(cnb-tools) $ cnb-tools submission info 9743445
         ID: 9743445
  Challenge: Challenge Portal Wiki Template
       Date: 2024-03-27
  Submitter: vchung

After

(cnb-tools-fix) $ cnb-tools submission info 9743445
         ID: 9743445
  Challenge: Challenge Portal Wiki Template
       Date: 2024-03-27
  Submitter: vchung