TRX className for generic test classes differs between source-generated and reflection modes #7151

What I saw

While running tests/TUnit.TestProject (net10.0, Release) with --treenode-filter "/*/TUnit.TestProject.Bugs._7106/*/*" --report-trx in each mode, the TRX className for tests on generic classes is different:

• Source-generated mode: TUnit.TestProject.Bugs._7106.GenericClassSameTypeRows1`
• Reflection mode (--reflection): TUnit.TestProject.Bugs._7106.GenericClassSameTypeRows1[[System.Int32, System.Private.CoreLib, Version=10.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]`

Every generic class in Bugs/_7106 shows the same split. In reflection mode, rows that infer different type arguments are also split across several class names (GenericClassMixedTypeRows1[[System.Int32...]]and...[[System.String...]]`), while source-generated mode groups them under one name.

Found while working on #7123 (PR #7150). The difference is not related to that change.

Repro

cd tests/TUnit.TestProject
dotnet build -c Release -f net10.0
bin/Release/net10.0/TUnit.TestProject.exe --treenode-filter "/*/TUnit.TestProject.Bugs._7106/*/*" --report-trx --report-trx-filename sg.trx
bin/Release/net10.0/TUnit.TestProject.exe --treenode-filter "/*/TUnit.TestProject.Bugs._7106/*/*" --reflection --report-trx --report-trx-filename refl.trx

Compare the className= attributes in the two files.

Expected

The same class name in both modes, so that TRX consumers and CI test-history grouping see the same identity whichever mode runs. The likely source is the type name that reaches the TRX reporter (TestMethodIdentifierProperty in src/TUnit.Engine/Extensions/TestExtensions.cs, or the closed Type that reflection mode reports). This needs checking against the #6433 decision on the type-name format.