* Feature combo orders
- Add support for combo orders
* Make fill model wait for all grouped orders to emit fills
* Add ComboFill to model multiple fills for combo orders
* Fill combo limit orders
Add some regression algorithms
* Add fill implementation for combo leg limit orders
* Add IFill as common interface for Fill and ComboFill
* Refactor combo orders removing IGroupOrder interface
Move the group order manager to the base Order class
* Update algorithms
* Handle combo order events atomically
* Refactor brokerage transaction event handler
* Refactor combo fill models
* Process fills in batch
* Combo orders fill model tests
* Combo leg limit orders algorithm
* Regression algorithms cleanup
* Fill and combo fill classes cleanup
* Housekeeping
* Refactor equity fill model to derive from base fill model
* Address review changes request
* Handling the new types of orders in the OrderJsonConverter
* Add regression algorithm to test combo orders update/cancel
* Add regression algorithm to test combo orders update/cancel
* Housekeeping
* Address review changes request
* Minor changes
* Security transaction handler method for setting order request id
* Extend public interface for placing combo orders
* Combo order tickets demo algorithm python version
* Tweaks and updates
* Minor fixes
* Minor changes
* Minor fixes
* Address reviews minor fixes
* Minor fixes
Co-authored-by: Martin-Molinero <martin@quantconnect.com>