Replaces the switch cases that can be replaces with switch expressions and removes `break;` where it isn't needed. https://dart.dev/language/branches#switch-statements
behavior_tree
flame_behavior_tree
First pass on adding behavior tree for flame. This PR adds 2 packages: - behavior_tree: A pure dart implementation of behavior tree. - flame_behavior_tree: A bridge package that integrates behavior_tree with flame. Demo: https://github.com/flame-engine/flame/assets/33748002/1d2b00ab-1b6e-406e-9052-a24370c8f1ab