Changes:
* Ensure IIS managed and pkg projects build after the native projects
* Update projects to build test
* Update CI checks to build on macOS and Linux
* Use package baselines to manage ANCM packages
This changes the way Microsoft.AspNetCore.App works to follow patterns set by Microsoft.NETCore.App. Instead of being a metapackage with dozens of dependencies, this package has no dependencies. It uses RID-splitting to deliver standalone assets for self-contained deployments.
Changes:
* Implements RID-split packages for Microsoft.AspNetCore.App.
* Update shared fx deps.json generation to only include entries for the RID-specific metapackages
* Include platform-specific packages in publish output
* Remove all nuspec dependencies of Microsoft.AspNetCore.App and collect all references into the package.