wix: use original version string for MSI filename
Version string normalization is mostly to placate MSI requirements.
I think it makes sense to use the original version string in
filenames.
Since we can have distinct versions normalizing to the same MSI
version string, this will allow us to distinguish between different
actual version strings based on the filename.
Differential Revision: https://phab.mercurial-scm.org/D8005