Fixes #3477: Fix debugger attach

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r27863 [[BR]]
In order to properly connect to debuggers like STAT, we need to get the hostname in its unstripped version for the MPIR_proctab. Unfortunately, we need a stripped version for Cray's alps launcher. So when we are stripping the hostname prefix, retain alias hostnames and add the ability to specify an alias to use in the proctab.