ShellExecute on a .zip file fails because the command in the registry
uses rundll32 that passes in an ANSI string, which is the default for
exported functions without a W suffix.
- This should also fix RAPPS not being able to open downloaded .zip files
- I made it use the full path to Explorer for good measure
Fixes regression introduced by 0.4.15-dev-6343-g bf2cec186c (#5411)
CORE-19506