<valarray>: `slice_array`/`gslice_array` incorrectly bind to function arguments of type `slice`/`gslice`

Describe the bug

MSVC STL's slice_array and gslice_array derive from slice and gslice, respectively.
https://github.com/microsoft/STL/blob/47cd70315d560e4fe1ac699c0eb8ec8bfc5cb658/stl/inc/valarray#L1382-L1384
https://github.com/microsoft/STL/blob/47cd70315d560e4fe1ac699c0eb8ec8bfc5cb658/stl/inc/valarray#L1560-L1562

When a function overload set with an overload for both valarray<bool> and slice is called with a slice_array<bool> argument, the valarray<bool> overload should be selected (slice_array<bool> is implicitly convertible to valarray<bool>) according to the standard. However, with MSVC STL, the slice overload is incorrectly selected because it is the base class of slice_array<bool>, and derived-to-base conversion is better than user-defined conversion in overload resolution.

Command-line test case

D:\Temp>type slice.cpp

#include <cassert>
#include <valarray>
using namespace std;

int main() {
    valarray<int> a(10);
    valarray<bool> b(false, 20);
    valarray<int> c = a[b[slice(0, 10, 2)]];
    assert(c.size() == 0);
    return 0;
}

D:\Temp>cl /EHsc /W4 /WX slice.cpp
Microsoft (R) C/C++ Optimizing Compiler Version 19.28.29812 for x64
Copyright (C) Microsoft Corporation.  All rights reserved.

slice.cpp
Microsoft (R) Incremental Linker Version 14.28.29812.0
Copyright (C) Microsoft Corporation.  All rights reserved.

/out:slice.exe
slice.obj

D:\Temp>.\slice.exe
Assertion failed: c.size() == 0, file slice.cpp, line 9

STL version

https://github.com/microsoft/STL/commit/c7b14059332afcc512ba245390bb0acf5bbbb0ed

Additional context

This bug is discovered when reviewing #1627, where slice_array<int> == slice_array<int> incorrectly calls the newly added operator==(const slice&, const slice&).

vNext note: Resolving this issue will require breaking binary compatibility. We won't be able to accept pull requests for this issue until the vNext branch is available. See #169 for more information.

Start with stl/inc/valarray at the slice_array and gslice_array definitions linked in the issue, then run the provided slice.cpp command-line test case. The fix is blocked until the vNext branch is available because it requires breaking binary compatibility; done means the valarray overload is selected instead of the slice overload.