fix(windows): create Keyman/Diag folder in redirected profile

Fixes #6221.

If Keyman is being installed under the SYSTEM profile, e.g. when using
tools such as SCCM or Intune, then the installer runs with a redirected
folder for %LocalAppData%, under C:\Windows\SysWow64\config, but is
given the name C:\Windows\System32\config\....

Keyman Setup then creates %LocalAppData%\Keyman\Diag, which it thinks is
in C:\Windows\System32\config\... But in reality it is in SysWow64\...
Keyman Setup passes a file under this folder to Windows Installer,
running as 64 bit, which immediately falls over because the path does
not exist to it, in the real System32\config folder.

This patch disables redirection temporarily just to create the folder
under both 32 and 64 bit versions of the profile. It has no effect on
normal user accounts (apart from verifying that the folder is present
twice rather than once).