Highly probable memory leak with VM::push / VM::pop

[poteto]

We currently push objects onto the stack via Vec::insert, which pushes all elements after it to the right. When we pop we don't remove the object from the stack, only decrementing the stack pointer. The VM therefore cannot reclaim popped objects from the stack because they keep getting shifted to the right.

[JamieCrisman]

I didn't test it much other than making sure it didn't break my implementations tests, but remove might work in this case. Though if you actually delete it from the stack, you'll need to keep track of the last popped separately since that method is expecting the data to still be in the stack.