Make TestAssets.sln buildable locally

[Youssef1313]

Description

• Considers artifacts/packages/CONFIGURATION/Shipping as package source
• Also considers $(Version)-dev which is the version generated in most local builds.
• When actually running the integration tests, the version is set by

  vstest/test/Microsoft.TestPlatform.Acceptance.IntegrationTests/Build.cs

  Line 62 in 3ae44f0

  ExecuteApplication2(Dotnet, $"""restore --packages {nugetCache} {nugetFeeds} --source "{IntegrationTestEnvironment.LocalPackageSource}" -p:PackageVersion={netTestSdkVersion} "{testAssets}" """);

Related issue

Kindly link any related issues. E.g. Fixes #xyz.

• I have ensured that there is a previously discussed and approved issue.

[Copilot]

Pull request overview

This PR makes the TestAssets.sln buildable locally by configuring the build to find locally built packages and use the appropriate version suffix for local builds.

Changes:

• Adds the local artifacts shipping directory as a package restore source
• Sets PackageVersion to $(Version)-dev to match the version format generated in local builds

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
test/TestAssets/Directory.Build.props	Adds the local artifacts/packages directory as an additional NuGet restore source
test/TestAssets/Directory.Build.targets	Sets PackageVersion to $(Version)-dev to align with locally built package versions

[Copilot]

Setting PackageVersion unconditionally will override the version set by the integration test infrastructure (via Build.cs) when the tests are run in CI. This property should only be set when a local build is detected, for example by conditioning on whether the local packages directory exists or on a property that indicates a local build, similar to the condition used in Directory.Build.props for RestoreAdditionalProjectSources. Without a condition, CI builds may end up using the wrong package version.

Suggested change

	<PropertyGroup>
	<PropertyGroup Condition="'$(IsLocalBuild)' == 'true'">