Test projects don't support csproj, dependencies or multitarget preferences

[michael-hawker]

Describe the bug

For samples we allow adding extra dependencies that are needed to showcase things just in the samples (but not required by the base component).

However, we don't have this same setup for the tests.

For instance, in DataTable it doesn't required the HeaderedControls, but we'd like to test against them still.

Steps to reproduce

N/A

Expected behavior

Able to add framework specific dependencies for UWP/WASDK to a test project within a component.

Screenshots

No response

Code Platform

• [X] UWP
• [X] WinAppSDK / WinUI 3
• [ ] Web Assembly (WASM)
• [ ] Android
• [ ] iOS
• [ ] MacOS
• [ ] Linux / GTK

Windows Build Number

• [ ] Windows 10 1809 (Build 17763)
• [ ] Windows 10 1903 (Build 18362)
• [ ] Windows 10 1909 (Build 18363)
• [ ] Windows 10 2004 (Build 19041)
• [ ] Windows 10 20H2 (Build 19042)
• [ ] Windows 10 21H1 (Build 19043)
• [ ] Windows 11 21H2 (Build 22000)
• [ ] Other (specify)

Other Windows Build number

No response

App minimum and target SDK version

• [ ] Windows 10, version 1809 (Build 17763)
• [ ] Windows 10, version 1903 (Build 18362)
• [ ] Windows 10, version 1909 (Build 18363)
• [ ] Windows 10, version 2004 (Build 19041)
• [ ] Other (specify)

Other SDK version

No response

Visual Studio Version

No response

Visual Studio Build Number

No response

Device form factor

No response

Additional context

No response

Help us help you

Yes, but only if others can assist.

[Arlodotexe]

We should probably just support .csproj alongside .shproj as outlined here: https://github.com/CommunityToolkit/Tooling-Windows-Submodule/issues/62#issuecomment-1588204934

[Arlodotexe]

csproj support in tests would also enable MultiTarget support, which would allow us to disable running component tests on unsupported test heads and avoid the need or workarounds like this: https://github.com/CommunityToolkit/Labs-Windows/commit/b3cf49070b1917059b35112964102d9a91e9599e