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: https://github.com/godotengine/godot-proposals/issues/3948#issuecomment-1037289197
2. Random.pick() will go along with Random.pop()
   • There's a similar PR with similar name in Godot:
   • https://github.com/godotengine/godot/pull/57007
   • pop() suggested in the proposal:
   • godotengine/godot-proposals#3454
3. Faster and easier to type.