dotnet test for MTP: Support TestTfmsInParallel

[Youssef1313]

Fixes #47496

TestTfmsInParallel was already supported in MTP with the old dotnet test as we are hooking into existing VSTest infrastructure. This brings feature parity.

[Copilot]

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• test/TestAssets/TestProjects/TestProjectWithMultipleTFMsParallelization/TestProject/TestProject.csproj: Language not supported
• test/TestAssets/TestProjects/TestProjectWithMultipleTFMsParallelization/TestProjectWithMultipleTFMsParallelization.sln: Language not supported
• test/TestAssets/TestProjects/TestProjectWithMultipleTFMsParallelization/dotnet.config: Language not supported

[nohwnd]

Can you fill in more details about the motivation, here or in the issue that is being fixed? Is this customer ask? Is this feature partity with vstest? To me the behavior of not running test projects in parallel when parallel run is enabled (default) seems undesirable, so I am probably missing some context.

[Youssef1313]

Can you fill in more details about the motivation, here or in the issue that is being fixed? Is this customer ask? Is this feature partity with vstest? To me the behavior of not running test projects in parallel when parallel run is enabled (default) seems undesirable, so I am probably missing some context.

Some projects access shared database and/or file system, for which case users are setting TestTfmsInParallel to false. This already works in MTP for the existing dotnet test and I came across users relying on it, so this reduces friction when moving from the old dotnet test for MTP to the new one. See microsoft/testfx#4392 for example.