Add advanced rules for conflict resolution in collider rule stage

[this-is-sofia]

At the moment, we implemented basic conflict resolution strategies for the collider rule stage in the PC algorithm (orientation rules -> collider test), namely:

• KEEP_FIRST: If an edge in an unshielded triple has been oriented as a collider and it is then attempted to be oriented as part of a second unshielded triple, the first orientation is kept and the other edge in the second unshielded triple is not oriented.
• KEEP_LAST: Works analogously with flipped order.

However, there are several enhancements that can be implemented:

• If an edge is trying to be oriented as part of a second unshielded triple and the orientations are compatible, i.e. x -> z <- y and x -> a <- y, orient both and not just the first or the last.
• If there are several options, choose the one with the highest probability (see e.g. causal learn's priority functions for a reference: https://github.com/py-why/causal-learn/blob/main/causallearn/utils/PCUtils/UCSepset.py)