Stop lowercasing module file names sometimes

[Mattwmaster58]

This is a suggestion for how to fix dotnet/diagnostics#5835.

I don't understand the codebase in depth so I'm really not sure this is the correct fix. But what I do know is that speedscope casing is now consistent. Empirically, it looks like this constructor where the module name is lowercases is used some portion of the time, and then other times the correctly case module name is used via some other codepath. But that's just a guess.

Here's a random example before. Unfortunately, the speedscope files are too big, so screenshots of speedscope.app is all I can easily provide:

Old behavior. Notably, most of the modules are correctly cased, but not all:

Behavior with this patch (modules consistently case, speedscope can correctly group calls together, color consistently, etc)