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/Controllers/BackOfficeServerVariables.cs

@@ -259,10 +259,6 @@ namespace Umbraco.Cms.Web.BackOffice.Controllers
                             "memberApiBaseUrl", _linkGenerator.GetUmbracoApiServiceBaseUrl<MemberController>(
                                 controller => controller.GetByKey(Guid.Empty))
                         },
-                        {
-                            "packageInstallApiBaseUrl", _linkGenerator.GetUmbracoApiServiceBaseUrl<PackageInstallController>(
-                                controller => controller.Fetch(string.Empty))
-                        },
                         {
                             "packageApiBaseUrl", _linkGenerator.GetUmbracoApiServiceBaseUrl<PackageController>(
                                 controller => controller.GetCreatedPackages())