Refactored BottleneckLowestPoint calculation

[Wully616]

I reused the GetSlopeDirection function to figure out the direction vector the bottleneck plane was sloping towards.
Using this and the position of the bottleneck and the radius of the bottleneck I projected a position along the slope direction

You can see the yellow Debug.Line() always points to the lowest point on the bottleneck plane
https://gyazo.com/8c758804ec17321f9dd7fdcb904b3b65

The performance improvements are pretty good too, I tested by spawning 64 infinite liquid bottles angled so the function is called.
It reduces the GC allocation to 0B and the function self ms from ~2.8ms to < 0.1ms

https://i.imgur.com/C0LJNh1.png

[Macoron]

Damn, that awesome! I will test and pull it asap