fix: shorten GetPipeName() output causing Unix crash

[Thundernerd]

This is a hotfix to combat the hard crash on unix machines which was introduced by e0e2ab6

On Unix machines the NamedPipeServerStream is created with a Path.GetTempPath() and "CoreFXPipe_" prefix, causing the recent change to go over the maximum length of the pipename of 104 characters: dotnet Unix PipeStream sourcecode.

Note
In the case of a long username this can still break as we now add an extra 16 characters from the hash to this pipe name.

Closes #2576

[JC-Chung]

Sorry for not considering the length limit when making this change in the first place.

One follow-up thought: would it make sense to also shorten the hash from 16 characters to something like 8 characters? That would give us even more headroom against the Unix domain socket path length limit, while still keeping the collision probability low enough for normal use cases.

Thanks for the fix!

[Thundernerd]

@JC-Chung no worries, it happens! Shortening the hash would definitely help yes. I think anything that can be shortened will help :D

[gadfly3173]

The target branch should be develop

[Thundernerd]

Closing in favor of #2585 with correct target branch, unable to modify it in this one.