Implements unattended package migrations for both explicit and implicit migrations (#10418)

* Clean up and changes to backoffice for the nuget only packages

* temp commit of package logic removal

* Lots of package code cleanup and removal

* Removes old package data from the test package xml

* Updates packaging code to take in XDocument instead of a file since we'll not be dealing with files, starts creating expressions for the package migrations scripting.

* fixing tests

* Fixes runtime state and boot failed middleware so that it actually runs. Separates out unattended install/upgrade into notification handlers.

* Gets unattended package migrations working and running

* Gets embedded package.xml resources able to install from package migration.

* Implements automatic package migrations for package that just declare an xml data manifest.

* fix build

* small cleanups

* fix build

* adds some tests

* Fix export test

* Fix newlines in test for linux

* Typo

* removes old todos and updates AutomaticPackgeMigrationPlan to use getter with backing field.

Co-authored-by: Bjarke Berg <mail@bergmania.dk>

src/Umbraco.Web.BackOffice/Install/InstallController.cs

@@ -1,4 +1,4 @@
-using System.IO;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http.Extensions;
 using Microsoft.AspNetCore.Mvc;
@@ -68,6 +68,7 @@ namespace Umbraco.Cms.Web.BackOffice.Install
             if (_runtime.Level == RuntimeLevel.Run)
                 return Redirect(umbracoPath);
 
+            // TODO: Update for package migrations
             if (_runtime.Level == RuntimeLevel.Upgrade)
             {
                 // Update ClientDependency version and delete its temp directories to make sure we get fresh caches