Create internal .NET Project System SDK

[tmeschter]

Summary

We have a lot of build logic duplicated (or almost duplicated) across our different repositories. This leads to several issues:

• It is difficult to tell what logic is core to a particular piece of build infrastructure (signing, localization, VSIX/NuGet/NPM packaging, testing, etc.) and what is a repo-specific modification to meet a particular need.
• Standing up a new repo is difficult as you need to figure out what to copy from a different repo.
• As best practices and/or the core tooling change it is difficult to update all the repos.
• While we have similar patterns across all (well, most) of our repos we don't have a single location where our infrastructure patterns are documented.

To address these issues we should pull out the core .props, .targets, and PowerShell scripts used by our build into a NuGet-based SDK, and then update all of our repos to consume that SDK.

[trivalik]

sounds like https://github.com/dotnet/arcade/blob/main/Documentation/ArcadeSdk.md