Stabilize package versions (#14003)

* Mark all blobs as shipping
- available (though not discoverable) in public dotnetcli feed

* Stabilize package versions

* Remove assumption that Microsoft.AspNetCore.AzureAppServices.SiteExtension packages have same version
- Microsoft.AspNetCore.AzureAppServices.SiteExtension.3.0 ships
- Microsoft.AspNetCore.AzureAppServices.SiteExtension.3.0.x?? do not ship

* Make installer versions consistent
- VS.Redist.Common.AspNetCore.SharedFramework and ...TargetingPack packages are non-shipping
- everything else ships

nit: remove extra whitespace in .nuspec files for the packages

* Correct assumptions in framework unit tests
- tests sometimes do not calculate version properties as product projects do
- Microsoft.AspNetCore.App.Ref and ...Runtime packages may rev versions separately

* Fix last 2 `SharedFxTests` failures

* Correct Microsoft.AspNetCore.App* versions used in ProjectTemplates tests
- `$(SharedFxVersion)` is not useful in test projects due to stable versioning

* Add continue on error for test templates