Update .NET Windows orb to .NET 7 | Orbs

Update .NET Windows orb to .NET 7

vince.horst@tentwodigital.com

.NET SDK 7 is now in the standard channel, and it would be immensely useful to have it installed in the Windows orb.

matt.patera@yakimachief.com

I would also love to have this. Our .NET devs are holding off on update PRs because moving to 7 will break our builds.