[WIP] Fix retrieval of properties for current user

[Copilot]

Thanks for assigning this issue to me. I'm starting to work on it and will keep this PR's description up to date as I form a plan and make progress.

Original prompt

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This section details on the original issue you should resolve

<issue_title>How to get properties of the "current user"?</issue_title>
<issue_description>The documentation says, "pass null into this method, which gets the current user's ID." But there's no documented way to use the returned system ID to obtain the properties of the "current user." I cannot get a User object from this system ID, therefore I cannot get any other properties. In particular, I seek the login ID and display name for the "current user" -- the owner of this process -- for a collaboration feature in our app.

I can get a list of users from System::User::FindAllAsync(...), but how do I determine which of those users is the "current user"? I tried iterating through that vector, calling GetSystemIdForUser(user).id() for each, and comparing with the value returned by GetSystemIdForUser(nullptr).id(), but none of them compared equal.

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Document Details

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• ID: 1bd2dc05-fa79-6ac6-ee32-0be55fc989e6
• Version Independent ID: 018fe01b-738f-1f0f-e91f-784fed8e641d
• Content: SystemIdentification.GetSystemIdForUser(User) Method (Windows.System.Profile) - Windows UWP applications
• Content Source: winrt-api-build/xml/Windows.System.Profile/SystemIdentification.xml
• Product: uwp
• Technology: winrt-reference
• GitHub Login: @hickeys
• Microsoft Alias: hickeys</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes How to get properties of the "current user"? #1743

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