Detect Visual Studio in Windows packaging script

Instead of hardcoding a specific VS install, try sequentially:

- %VSINSTALLDIR% (already set from a vs prompt)
- 2019/Enterprise
- 2019/Professional
- 2019/Community
- 2019/BuildTools

It stops when one is found and set vsdevcmd env var.

Differential revision: https://reviews.llvm.org/D135173