dotnet-trace speedscope format does not case normalize correctly

When I'm using dotnet-trace, case normalization is applied inconsistently, and it appears we end up worse off than if there was no case normalization. The format doesn't matter - nettrace or speedscope both have the inconsistencies

eg dotnet-trace collect --profile cpu-sampling --format Speedscope --mydll.dll

### Regression?
Probably not from my cursory review of the code

### Other information

Practical effect of this is that speedscope viewers cannot group calls together:

[ablaze-20260508-102713.speedscope.json](https://github.com/user-attachments/files/27531139/ablaze-20260508-102713.speedscope.json)