[ASP.NET Core Integration] Add templates using 3-package approach

[satvu]

Resolves https://github.com/Azure/azure-functions-dotnet-worker/issues/1465

Validations:

• [x] Dotnet CLI
  • [x] NetFx
  • [x] NetCore
  • [x] Core Tools (following this flow)
  • [x] NetFx
  • [x] NetCore

VS validation will have to be done with a tooling-feed test to make sure NetFx and NetCore scenarios point to the correct package.

Additional Notes

• If you use the Core package in a net48 project context, it spits out the core version but the nuget install seems to fail silently - we do NOT expect this pattern as customers should not be mixing templates for different frameworks when using CLI or core-tools. This will be controlled on our end for VS.
  • The inverse of this also leads to failure (same error as in https://github.com/Azure/azure-functions-dotnet-worker/issues/2184), but that is also an unsupported/unexpected pattern.

[mattchenderson]

Also validated in VS Code, so I'm feeling good about this set of changes once the App Insights wire-up is back in there.

Edit: (and bumping package versions as needed)