Make array_view(pointer, size) constructor public

[dfields-msft]

Addressing #665 by promoting the array_view(pointer, size) constructor to be public rather than protected, which is consistent with C++20's std::span that winrt::array_view is designed to emulate.

[kennykerr]

/azp run

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[oldnewthing]

Please add a unit test and verify that the deduction guide works.

[dfields-msft]

@oldnewthing please let me know if the test I added is covering what you had in mind re: deduction guides.

[dfields-msft]

@kennykerr this formulation requires callers to explicitly cast to size_type which is done implicitly for all other constructors. Fixing this would be possible, but would require a bit of extra template goop and I know that you're sensitive to the overhead of this. Do you have an opinion on what the contract of this constructor should be?

[oldnewthing]

I was thinking of adding a new case to the com_array,ctad test:

    REQUIRE_DEDUCED_AS(uint8_t, { &a[0], 3 });

to verify that

com_array{ &a[0], 3 }

deduces as com_array<uint8_t>.

[dfields-msft]

@oldnewthing now I see what you're talking about; done.

[kennykerr]

/azp run

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[kennykerr]

Looks good. I just now saw your comment about size_type. C++/WinRT uses uint32_t for sizes consistent with WinRT. I'm not philosophically opposed to changing that, but it would cause ripples. Unless there's a strong reason to change it now, I'd rather hang in there until we can ditch it all in favor of std::span.