Accessibility issue with TabView control

[mrlacey]

Describe the bug

The TabView control fails basic accessibility tests because it does not implement the selection pattern.

Steps to reproduce the bug

1. Add a TabView control to a page

    <winui:TabView>
        <winui:TabViewItem Header="first"/>
        <winui:TabViewItem Header="second"/>
    </winui:TabView>

2. Run app
3. Test the app with Accessibility Insights for Windows

Expected behavior

The default behavior of the control should not contain anything that causes it to fail basic accessibility checks.
Specifically Section 508 502.3.10.

Screenshots

Version Info

NuGet package version: Microsoft.UI.Xaml 2.4.2

Windows 10 version	Saw the problem?
Insider Build (20175)	Yes
May 2020 Update (19041)	Yes
November 2019 Update (18363)
May 2019 Update (18362)
October 2018 Update (17763)
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop	Yes
Xbox
Surface Hub
IoT

Additional context

This was discovered while reviewing the accessibility of applications generated by Windows Template Studio. (microsoft/TemplateStudio#3723)

[marcelwgn]

This was fixed with #2856 .

[Felix-Dev]

@mrlacey This is fixed by PR #2856 I believe.

[mrlacey]

Closing as duplicate of #2856 but still happens with 2.5.0-prerelease.200708003