`STL.natvis`: `move_iterator` visualizer should use `_Current`, not `current`

[StephanTLavavej]

STL/stl/inc/xutility

Lines 4149 to 4152 in ef1d621

	_EXPORT_STD template <class _Iter>
	class move_iterator : public _Move_iterator_category<_Iter> {
	private:
	_Iter _Current{};

STL/stl/debugger/STL.natvis

Lines 1522 to 1527 in ef1d621

	<Type Name="std::move_iterator&lt;*&gt;">
	<DisplayString>move_iterator {current}</DisplayString>
	<Expand>
	<Item Name="current">current</Item>
	</Expand>
	</Type>

And traditionally, we've used Name="[current]" to indicate that we're displaying a pretty name for an ugly data member.

Regression introduced by #1080 on 2020-07-27 in VS 2019 16.8.

Reported by Xiang Fan (@xiangfan-ms).