Removed directory ... due to it not containing any tests

If you open an issue please include
1. Dotnet sdk version
3.1.102

2. Unit test framework and relevants versions of that
```

```
3. A link to a repo that replicated the issue
https://github.com/mjnorman/test-explorer-repro

The issue is that the Test Explorer does not recognize the Tests project. The repro was created by simply

```
dotnet new mvc -o MyProject.Web
dotnet new nunit -o MyProject.Tests
dotnet new sln
dotnet sln add HRMenu.Web/HRMenu.Web.csproj
dotnet sln add HRMenu.Tests/HRMenu.Tests.csproj
```
The log indicates:
```
Starting extension
Finding projects for pattern /test/**/*Tests.csproj
Found 1 matches for pattern in folder /test
Evaluating match /test/MyProject.Tests/MyProject.Tests.csproj
Adding directory /test/MyProject.Tests
Executing dotnet test -t -v=q --no-build /p:CollectCoverage=true /p:CoverletOutputFormat=lcov /p:CoverletOutput=./lcov in /test/MyProject.Tests
[WARNING] Removed directory /test/MyProject.Tests due to it not containting any tests

Start with the linked test-explorer-repro repository and reproduce the setup using the listed dotnet new and dotnet sln commands. Read the log around `dotnet test -t` and the removal warning; done means the NUnit project remains recognized in Test Explorer instead of being removed as empty.

Written by the indexing model from the issue text.