Add chain optimizations for Conditional nodes

[RunDevelopment]

The new optimization removes a Conditional node if:

1. its condition is a statically known constant, or
2. both the If True and If False inputs are connected to the same node.

Constant conditions aren't used right now, but they will be once the Condition inputs gets an input element in the UI.

---

I also changed the switch optimization to remove the Switch node instead of trimming other inputs. I did this, because it's a prerequisite for other optimizations.