Rename Random.choice() to Random.pick()

[Xrayez]

Part of #176.

1. To avoid name collision with Random.choices() for weighed selection.
   • If we were to add this to Godot, only Random.choices() would be likely merged: Add a method to get a random element with weighted probability (similar to random.choices() in Python) godotengine/godot-proposals#3948 (comment)
2. Random.pick() will go along with Random.pop()
   • There's a similar PR with similar name in Godot:
   • Implement Function: Array.pick_random() godotengine/godot#57007
   • pop() suggested in the proposal:
   • Add Array.pick_random() as a shorthand for Array[randi() % Array.size()] godotengine/godot-proposals#3454
3. Faster and easier to type.