[misp-feed] Update connector to be "manager_supported"

[Powlinett]

Proposed changes

• update Docker files
• implement BaseConnectorSettings from the connectors-sdk
• replace pycti.get_config_variables use by settings.py
• update connector.py
• update main.py
• update unit tests
• generate __metadata__/connector_config_schema.json

Related issues

• #4857

Checklist

• [x] I consider the submitted work as finished
• [x] I have signed my commits using GPG key.
• [x] I tested the code for its functionality using different use cases
• [ ] I added/update the relevant documentation (~~either on github or on notion~~ connector's README)
• [ ] ~~Where necessary I refactored code to improve the overall quality~~ (not needed)

Further comments

This connector has been migrated manually as the migration scripts always timeout with Misp Feed 🤷‍♀️