The MSI install scope was set to the WiX default, which is per-user.
However, with UAC, it could not be installed by a standard user because
InstallPrivileges is elevated by default, hence the install scope
should be set to per-machine. Furthermore, the default install path is
a per-machine location and setting the system path requires
administrator privileges.

By changing the InstallScope to perMachine, Start Menu shortcuts are
placed in ProgramData and not the installing user's AppData folder,
making the shortcuts available to other users. This also fixes the
installation when AppData is a network folder.

The custom action is necessary to allow upgrades. Since a per-machine
MSI cannot upgrade an application installed per-user, the custom action
checks if there is going to be an upgrade to a previous version
installed per-user and sets the installation as per-user to allow
upgrading. Hence, the advantages of installing per-machine will only
apply in fresh installations.

Fixes #5849
Fixes #7629

Since install is per machine only, installation path should be stored
in local machine instead of current user. The registry stores HKLM in
different places for 32 and 64 bit applications, so the installer will
not suggest the old path when upgrading from 32 to 64 bit version.

Fixes #5592
Fixes #25087

This test just failed on Ubuntu in Jenkins, for a change that
is 100% Windows-specific.