[Bootstrapper] Add logic for Global.Json

[nagilson]

📓 Summary

Global.json parsing should be added to install the SDK. We don't have a great idea of how this should work and what it should do yet. Or if we should auto install etc based on the global.json and how the user interacts with this. Or, how will rollFoward compare with the channel version support. And, what types of versions of dotnet do we support? (8.0.1xx, fully specified, major.minor, major?)

Additional Context

Supporting local SDK deployment in global.json by jaredpar · Pull Request #303 · dotnet/designs We may want to utilize this design.

There should be a lot of pre-existing code to interface with global.json. Make sure you aren't rewriting the world.

Consider that global.json may be in upper directories or child directories and how it should or shouldn't be applied.

Blocked Until These Issues Are Done:

#358