refactor(ingest/kafka-connect): define interface for new connector impl

[mayurinehate]

• Separate kafka_connect module and update setup.py
• Split existing large file into module
  • common.py for config, report, shared data models, BaseConnector superclass for all connectors to define explicit implementations needed for new connector
  • source_connectors.py for all source connector implementations.
  • sink_connectors.py for all sink connector implementations
  • kakfa_connect.py for core control flow and aspect generation logic
• Some minor edits - for example remove __eq__ usage

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable). If a new feature has been added a Usage Guide has been added for the same.
• For any breaking change/potential downtime/deprecation/big changes an entry has been made in Updating DataHub

[mayurinehate]

CI failures are unrelated