Octobot-channels

Fixed
- Channel is_paused attribute to public

Added
- Producer pause and resume methods
- Channel producers pause/resume management

Related issue
- [Producer] Implement channel pause and resume 8

Fixed
- Channel init_consumer_if_necessary object key type

Fixed
- Channel init_consumer_if_necessary iterable type

Added
- Channel global tests

Changed
- Migrate Consumer start, run and stop methods to async

Fixed
- Consumer attributes queue and filter_size to public
- Channel start and stop methods
- Channels methods Cython compliance

Changed
- PyDoc fixes