Switch RhConfig from TCHAR to char

[elinor-fung]

I didn't see a reason for NativeAOT's RhConfig to be use TCHAR - wchar_t on windows, char otherwise. We can hide away the details of reading the environment variable as wchar vs char and the embedded variables are embedded as ASCII (and read as such) already. This makes it stop using TCHAR for the exposed API which seemed to just be more confusing to consume (this also makes it so that RhConfig.h no longer just assumes some header included before it defines TCHAR/_T).

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Issue Details

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I don't think there's any reason for NativeAOT's RhConfig to use TCHAR - defined to be wchar_t on windows, char otherwise. We shouldn't need to read the environment variable as wide characters and the embedded variables are embedded as ASCII (and read as such) already, so having the split seemed to just make it be more confusing to consume and implement (also makes it so that RhConfig.h no longer just assumes some header included before it defines TCHAR/_T)

Author:	elinor-fung
Assignees:	-
Labels:	area-NativeAOT-coreclr
Milestone:	-

[LakshanF]

Thanks for doing this! I assume we will test this more once EventPipe configuration option is enabled

[jkotas]

You can also delete TCHAR definition from src\coreclr\gc\env\gcenv.structs.h. I think it was there to make this work.

[elinor-fung]

Seems like some other parts of nativeaot are actually using the definition from there now. I might try to detangle in the future change, but I'm going to leave it for now.