[swift] LeetCode 283. Move Zeroes

Given an array nums, write a function to move all 0’s to the end of it while maintaining the relative order of the non-zero elements.

For example, given nums = [0, 1, 0, 3, 12], after calling your function, nums should be [1, 3, 12, 0, 0].

You must do this in-place without making a copy of the array.
Minimize the total number of operations.
Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.