Support for .NET 8 and MSTest.TestAdapter in TeamCity fails due to outdated VSTest integration (vstest15)

We are facing an issue running MSTest tests targeting .NET 8 in TeamCity seemingly due to the lack of a compatible TestAdapter and outdated VSTest integrations.

When running MSTest unit tests in TeamCity using the .NET runner, TeamCity attempts to invoke vstest15 from the build agent's plugins directory:

`C:\BuildAgent\plugins\dotnet\tools\vstest15`

This fails because the vstest15 integration appears outdated and incompatible with Visual Studio 2022 and .NET 8.

```
Could not load type 'Microsoft.VisualStudio.TestTools.UnitTesting.StringEx'
from assembly 'Microsoft.VisualStudio.TestPlatform.TestFramework, Version=14.0.0.0'
```

If it is a compatibility problem, are you planning on updating the Test Adapter to support .NET 8? Else, please provide guidance on resolving this issue.

## Temporary Workaround
We've found a temporary workaround in simply invoking it through a Powershell script instead, however it's far from ideal since test results are not properly parsed or displayed in the TeamCity UI. Parsing build logs manually is error-prone and time-consuming.
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**Note** it is working as expected on our NET 4.8 projects.