CmdPal: Icon cache (#44538)

## Summary of the Pull Request

This PR implements actual cache in IconCacheService and adds some fixes
on top for free.

The good
- `IconCacheService` now caches decoded icons
- Ensures that UI thread is not starved by loading icons by limiting
number of threads that can load icons at any given time
- `IconCacheService` decodes bitmaps directly to the required size to
reduce memory usage
- `IconBox` now reacts to theme, DPI scale, and size changes immediately
- Introduced `AdaptiveCache` with time-based decay to improve icon reuse
- Updated `IconCacheProvider` and `IconCacheService` to handle multiple
icon sizes and scale-aware caching
- Added priority-based decoding in `IconCacheService` for more
responsive loading
- Extended `IconPathConverter` to support target icon sizes
- Switched hero images in `ShellPage` to use the jumbo icon cache
- Made `MainWindow` title bar logic resilient to a null `XamlRoot`
- Fixed Tag icon positioning
- Removes custom `TypedEventHandlerExtensions` in favor of
`CommunityToolkit.WinUI.Deferred`.

The bad
- Since IconData lacks a unique identity, when it includes a stream, it
relies on simple reference equality, acknowledging that it might not be
stable. We might cache some obsolete garbage because of this, but it is
fast and better than nothing at all. Yet another task for the future me.

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## PR Checklist

- [ ] Closes: 
- [ ] Closes: #38284
- [ ] Related to: #44407
- [ ] Related to: https://github.com/zadjii-msft/PowerToys/issues/333
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

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or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

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wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

src/modules/cmdpal/Microsoft.CmdPal.UI/Helpers/Icons/IconCacheProvider.cs

@@ -0,0 +1,79 @@
+// 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 Microsoft.CmdPal.Core.ViewModels;
+using Microsoft.CmdPal.UI.Controls;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Microsoft.CmdPal.UI.Helpers;
+
+/// <summary>
+/// Common async event handler provides the cache lookup function for the <see cref="IconBox.SourceRequested"/> deferred event.
+/// </summary>
+public static partial class IconCacheProvider
+{
+    /*
+      Memory Usage Considerations (raw estimates):
+      | Icon Size | Per Icon | Count |    Total | Per Icon @ 200% | Total @ 200% | Per Icon @ 300% | Total @ 300% |
+      | --------- | -------: | ----: | -------: | --------------: | -----------: | --------------: | -----------: |
+      | 20×20     |   1.6 KB |  1024 |   1.6 MB |          6.4 KB |       6.4 MB |         14.4 KB |      14.4 MB |
+      | 32×32     |   4.0 KB |   512 |   2.0 MB |           16 KB |       8.0 MB |         36.0 KB |      18.0 MB |
+      | 48×48     |   9.0 KB |   256 |   2.3 MB |           36 KB |       9.0 MB |         81.0 KB |      20.3 MB |
+      | 64×64     |  16.0 KB |    64 |   1.0 MB |           64 KB |       4.0 MB |        144.0 KB |       9.0 MB |
+      | 256×256   | 256.0 KB |    64 |  16.0 MB |            1 MB |      64.0 MB |          2.3 MB |       144 MB |
+    */
+
+    private static IIconSourceProvider _provider20 = null!;
+    private static IIconSourceProvider _provider32 = null!;
+    private static IIconSourceProvider _provider64 = null!;
+    private static IIconSourceProvider _provider256 = null!;
+
+    public static void Initialize(IServiceProvider serviceProvider)
+    {
+        _provider20 = serviceProvider.GetRequiredKeyedService<IIconSourceProvider>(WellKnownIconSize.Size20);
+        _provider32 = serviceProvider.GetRequiredKeyedService<IIconSourceProvider>(WellKnownIconSize.Size32);
+        _provider64 = serviceProvider.GetRequiredKeyedService<IIconSourceProvider>(WellKnownIconSize.Size64);
+        _provider256 = serviceProvider.GetRequiredKeyedService<IIconSourceProvider>(WellKnownIconSize.Size256);
+    }
+
+    private static async void SourceRequestedCore(IIconSourceProvider service, SourceRequestedEventArgs args)
+    {
+        if (args.Key is null)
+        {
+            return;
+        }
+
+        var deferral = args.GetDeferral();
+
+        try
+        {
+            args.Value = args.Key switch
+            {
+                IconDataViewModel iconData => await service.GetIconSource(iconData, args.Scale),
+                IconInfoViewModel iconInfo => await service.GetIconSource(
+                    args.Theme == Microsoft.UI.Xaml.ElementTheme.Light ? iconInfo.Light : iconInfo.Dark,
+                    args.Scale),
+                _ => null,
+            };
+        }
+        finally
+        {
+            deferral.Complete();
+        }
+    }
+
+#pragma warning disable IDE0060 // Remove unused parameter
+    public static void SourceRequested20(IconBox sender, SourceRequestedEventArgs args)
+        => SourceRequestedCore(_provider20, args);
+
+    public static void SourceRequested32(IconBox sender, SourceRequestedEventArgs args)
+        => SourceRequestedCore(_provider32, args);
+
+    public static void SourceRequested64(IconBox sender, SourceRequestedEventArgs args)
+        => SourceRequestedCore(_provider64, args);
+
+    public static void SourceRequested256(IconBox sender, SourceRequestedEventArgs args)
+        => SourceRequestedCore(_provider256, args);
+#pragma warning restore IDE0060 // Remove unused parameter
+}