STL.natvis: `make_shared` and `allocate_shared` are no longer visualized properly

[StephanTLavavej]

STL.natvis contains visualizers for _Ref_count_obj and _Ref_count_obj_alloc:

STL/stl/debugger/STL.natvis

Lines 396 to 401 in 9947dd9

	<Type Name="std::_Ref_count_obj&lt;*&gt;">
	<DisplayString>make_shared</DisplayString>
	<Expand>
	<Item Condition="_Uses != 0" Name="[original ptr]">($T1 *) &amp;_Storage</Item>
	</Expand>
	</Type>

STL/stl/debugger/STL.natvis

Lines 412 to 419 in 9947dd9

	<!-- VC 2015 -->
	<Type Name="std::_Ref_count_obj_alloc&lt;*&gt;">
	<DisplayString>allocate_shared</DisplayString>
	<Expand>
	<Item Condition="_Uses != 0" Name="[original ptr]">($T1 *) &amp;_Mypair._Myval2</Item>
	<Item Name="[allocator]">_Mypair</Item>
	</Expand>
	</Type>

However, we've upgraded those control blocks (which is possible while preserving binary compatibility because shared_ptr performs type erasure). The modern forms are _Ref_count_obj2 and _Ref_count_obj_alloc3, which we don't have visualizers for:

STL/stl/inc/memory

Lines 2018 to 2019 in 9947dd9

	template <class _Ty>
	class _Ref_count_obj2 : public _Ref_count_base { // handle reference counting for object in control block, no allocator

STL/stl/inc/memory

Lines 2438 to 2439 in 9947dd9

	template <class _Ty, class _Alloc>
	class _Ref_count_obj_alloc3 : public _Ebco_base<_Rebind_alloc_t<_Alloc, _Ty>>, public _Ref_count_base {

Thus, while we intended for make_shared and allocate_shared to be visualized in cool ways, this has been broken for a while.