Evaluate probabilistic operators shared preconditions once

[Maumagnaguagno]

Shared preconditions can be optimized to be evaluated only once, which may require modifications in both UHyper_Compiler#compile_domain and Hypertension_U#planning.
This process can be done by:

• Only evaluating the preconditions during the first outcome evaluation
• Separating preconditions from operator application (using N + 1 methods)
• Using coroutines.

May be slower when evaluating a complex precondition before minimum probability!
See Hypertension_U#execute.