Rename the [Ee]xts dir to ext (#38852)

**WARNING:** This PR will probably blow up all in-flight PRs

at some point in the early days of CmdPal, two of us created seperate
`Exts` and `exts` dirs. Depending on what the casing was on the branch
that you checked one of those out from, it'd get stuck like that on your
PC forever.

Windows didn't care, so we never noticed.

But GitHub does care, and now browsing the source on GitHub is basically
impossible.

Closes #38081

src/modules/cmdpal/ext/Microsoft.CmdPal.Ext.Indexer/Pages/IndexerPage.cs

@@ -0,0 +1,127 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Threading.Tasks;
+using ManagedCommon;
+using Microsoft.CmdPal.Ext.Indexer.Data;
+using Microsoft.CmdPal.Ext.Indexer.Indexer;
+using Microsoft.CmdPal.Ext.Indexer.Properties;
+using Microsoft.CommandPalette.Extensions;
+using Microsoft.CommandPalette.Extensions.Toolkit;
+using Windows.Storage.Streams;
+
+namespace Microsoft.CmdPal.Ext.Indexer;
+
+internal sealed partial class IndexerPage : DynamicListPage, IDisposable
+{
+    private readonly List<IListItem> _indexerListItems = [];
+
+    private SearchQuery _searchQuery = new();
+
+    private uint _queryCookie = 10;
+
+    public IndexerPage()
+    {
+        Id = "com.microsoft.indexer.fileSearch";
+        Icon = Icons.FileExplorer;
+        Name = Resources.Indexer_Title;
+        PlaceholderText = Resources.Indexer_PlaceholderText;
+    }
+
+    public override void UpdateSearchText(string oldSearch, string newSearch)
+    {
+        if (oldSearch != newSearch)
+        {
+            _ = Task.Run(() =>
+            {
+                Query(newSearch);
+                LoadMore();
+            });
+        }
+    }
+
+    public override IListItem[] GetItems() => [.. _indexerListItems];
+
+    public override void LoadMore()
+    {
+        IsLoading = true;
+        FetchItems(20);
+        IsLoading = false;
+        RaiseItemsChanged(_indexerListItems.Count);
+    }
+
+    private void Query(string query)
+    {
+        ++_queryCookie;
+        _indexerListItems.Clear();
+        _searchQuery.SearchResults.Clear();
+        _searchQuery.CancelOutstandingQueries();
+
+        if (query == string.Empty)
+        {
+            return;
+        }
+
+        Stopwatch stopwatch = new();
+        stopwatch.Start();
+
+        _searchQuery.Execute(query, _queryCookie);
+
+        stopwatch.Stop();
+        Logger.LogDebug($"Query time: {stopwatch.ElapsedMilliseconds} ms, query: \"{query}\"");
+    }
+
+    private void FetchItems(int limit)
+    {
+        if (_searchQuery != null)
+        {
+            var cookie = _searchQuery.Cookie;
+            if (cookie == _queryCookie)
+            {
+                var index = 0;
+                SearchResult result;
+
+                var hasMoreItems = _searchQuery.FetchRows(_indexerListItems.Count, limit);
+
+                while (!_searchQuery.SearchResults.IsEmpty && _searchQuery.SearchResults.TryDequeue(out result) && ++index <= limit)
+                {
+                    IconInfo icon = null;
+                    try
+                    {
+                        var stream = ThumbnailHelper.GetThumbnail(result.LaunchUri).Result;
+                        if (stream != null)
+                        {
+                            var data = new IconData(RandomAccessStreamReference.CreateFromStream(stream));
+                            icon = new IconInfo(data, data);
+                        }
+                    }
+                    catch (Exception ex)
+                    {
+                        Logger.LogError("Failed to get the icon.", ex);
+                    }
+
+                    _indexerListItems.Add(new IndexerListItem(new IndexerItem
+                    {
+                        FileName = result.ItemDisplayName,
+                        FullPath = result.LaunchUri,
+                    })
+                    {
+                        Icon = icon,
+                    });
+                }
+
+                HasMoreItems = hasMoreItems;
+            }
+        }
+    }
+
+    public void Dispose()
+    {
+        _searchQuery = null;
+        GC.SuppressFinalize(this);
+    }
+}