Remove duplicate remote server mediator code

[PaulHigin]

PR Summary

This PR removes duplicate server mediator classes, and refactors code to use a single mediator for StdIO based connections.
It also fixes parameter arguments so that configuration name is passed in correctly.

PR Context

There used to be two separate server mediator derivations, one each for OutOfProc and SSH transports. They both use StdIO for communication, but SSH had special code to deal with .NET implementation inconsistencies. But .NET addressed the issues and now both class derivations operate identically. So this PR creates a single StdIOProcessMediator class for both uses.

I also found a bug where the 'configurationName' parameter was not passed in correctly for HyperV mediators. I fixed the issues, but it turns out that the code path is not being used for PowerShellDirect VM connections, but I am not sure about container connections.
Actually, neither of these code paths are used because currently PowerShellDirect only works with WindowsPowerShell.

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[SteveL-MSFT]

LGTM, one suggestion

[ghost]

🎉v7.3.0-preview.1 has been released which incorporates this pull request.:tada:

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