Implements Examine/Lucene index syncing for use on Azure (#10386)

* Updates to latest examine, ensures indexes are unlocked on startup, adds more info to the diagnostics and allows for the new sync directory factory to work.

* Gets index syncing working correct and fixes reindexing to not overprocess indexes

* fix duplicate package ref

* rebuilds empty indexes and fixes config with enum

* missing file

src/Umbraco.Core/Configuration/Models/IndexCreatorSettings.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Umbraco.
 // See LICENSE for more details.
 
+using System;
+
 namespace Umbraco.Cms.Core.Configuration.Models
 {
     /// <summary>
@@ -11,6 +13,7 @@ namespace Umbraco.Cms.Core.Configuration.Models
         /// <summary>
         /// Gets or sets a value for lucene directory factory type.
         /// </summary>
-        public string LuceneDirectoryFactory { get; set; }
+        public LuceneDirectoryFactory LuceneDirectoryFactory { get; set; }
+
     }
 }

src/Umbraco.Core/Configuration/Models/LuceneDirectoryFactory.cs

@@ -0,0 +1,24 @@
+// Copyright (c) Umbraco.
+// See LICENSE for more details.
+
+namespace Umbraco.Cms.Core.Configuration.Models
+{
+    public enum LuceneDirectoryFactory
+    {
+        /// <summary>
+        /// The index will operate from the default location: Umbraco/Data/Temp/ExamineIndexes
+        /// </summary>
+        Default,
+
+        /// <summary>
+        /// The index will operate on a local index created in the processes %temp% location and
+        /// will replicate back to main storage in Umbraco/Data/Temp/ExamineIndexes
+        /// </summary>
+        SyncedTempFileSystemDirectoryFactory,
+
+        /// <summary>
+        /// The index will operate only in the processes %temp% directory location
+        /// </summary>
+        TempFileSystemDirectoryFactory
+    }
+}