Windows Installer machine needed for MSVC

Need a throw-away instance that we can start each time we want to package a new MSVC version.

Scripts in https://github.com/compiler-explorer/infra/tree/main/msvc-install were used to get a lot of versions, but is obviously not recommended for normal use.

Idea is to:
* launch a fresh instance
* pass the URL to an install script (called from a manual workflow?)
* it downloading the installer from that url
* install the buildtools
* rename the msvc compiler dir to `$compilerVersion-$productVersion`
* zip up that directory
* upload to s3
* shutdown

Possible problems:
* We'll only know the `productVersion` after the compiler has been installed (productVersion is unique, compilerVersion is not)
* So only after it's know you could use `msvc-install/gen-props.ps1` to see how the properties would look
* probably much more...