Windows SDK upgrade

[tymlipari]

For questions, please use the forum.

Describe the bug
The latest Github Actions agents for Windows no longer have the 10.0.18362.0 SDK available as it's several major versions behind. The related projects should be updated to target a newer version of the Windows SDK. Unfortunately upstream dependencies from react-native-windows (at least for 0.64) also include VS projects targeting that same build number.

To Reproduce
Steps to reproduce the behavior:

1. Clone the repository for Windows
2. Ensure the 18362 SDK is uninstalled and a newer version is installed
3. Observe the React Native build fail when running npm run windows for the Playground project targeting 0.64.

Suggested fix
For 0.64 it's unlikely RNW will update their package, but the CI builds can be scripted to scan all of the *.vcxproj files referenced (including those from npm modules) from the solution file and update their <WindowsTargetPlatformVersion/> elements to target a newer SDK version. This will have no runtime impact as all Windows SDKs are backwards compatible, but will allow the project to build with later SDKs.

[bghgary]

Duping with #507