Add runtime mode (BackofficeDevelopment, Development and Production) (#12631)

* Add runtime mode setting

* Only enable Razor runtime compilation in development modes

* Only enable ModelsBuilder generation in development modes

* Fix disabling ModelsBuilder controllers

* Add IRuntimeModeValidationService and IRuntimeModeValidator

* Add JITOptimizerValidator

* Add UmbracoApplicationUrlValidator

* Add UseHttpsValidator

* Add RuntimeMinificationValidator

* Add ModelsBuilderModeValidator

* Remove .NET 6 preview 1 fix for Razor runtime compilation

* Only allow InMemoryAuto in backoffice development mode

* Make runtime mode validators public, so they can be easily removed if required

* Add comment to highlight removing RazorCompileOnBuild, RazorCompileOnPublish and CopyRazorGenerateFilesToPublishDirectory when using ModelsMode InMemoryAuto

* Add documentation

* Update src/Umbraco.Web.Common/ModelsBuilder/NoopModelsBuilderDashboardProvider.cs

Co-authored-by: Ronald Barendse <ronald@barend.se>

Co-authored-by: Nikolaj Geisle <70372949+Zeegaan@users.noreply.github.com>

src/Umbraco.Core/Extensions/ConfigurationExtensions.cs

@@ -1,10 +1,11 @@
 using Microsoft.Extensions.Configuration;
 using Umbraco.Cms.Core;
+using Umbraco.Cms.Core.Configuration.Models;
 
 namespace Umbraco.Extensions;
 
 /// <summary>
-/// Extension methods for configuration.
+/// Extensions for <see cref="IConfiguration" />.
 /// </summary>
 public static class ConfigurationExtensions
 {
@@ -90,4 +91,14 @@ public static class ConfigurationExtensions
 
         return connectionString;
     }
+
+    /// <summary>
+    /// Gets the Umbraco runtime mode.
+    /// </summary>
+    /// <param name="configuration">The configuration.</param>
+    /// <returns>
+    /// The Umbraco runtime mode.
+    /// </returns>
+    public static RuntimeMode GetRuntimeMode(this IConfiguration configuration)
+        => configuration.GetValue<RuntimeMode>(Constants.Configuration.ConfigRuntimeMode);
 }