Create a Microsoft.CmdPal.Core.ViewModels project (#40560)

_targets #40504_ 

Major refactoring for #40113

This moves a large swath of the codebase to a `.Core` project. "Core"
doesn't have any explicit dependencies on "extensions", settings or the
current `MainListPage`. It's just a filterable list of stuff. This
should let us make this component a bit more reusable.

This is half of a PR. As I did this, I noticed a particular bit of code
for TopLevelVViewModels and CommandPaletteHost that was _very rough_.
Solving it in this PR would make "move everything to a new project" much
harder to review. So I'm submitting two PRs simultaneously, so we can
see the changes separately, then merge together.

src/modules/cmdpal/Microsoft.CmdPal.Core.ViewModels/CommandContextItemViewModel.cs

@@ -0,0 +1,49 @@
+// 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.Models;
+using Microsoft.CommandPalette.Extensions;
+
+namespace Microsoft.CmdPal.Core.ViewModels;
+
+public partial class CommandContextItemViewModel(ICommandContextItem contextItem, WeakReference<IPageContext> context) : CommandItemViewModel(new(contextItem), context), IContextItemViewModel
+{
+    private readonly KeyChord nullKeyChord = new(0, 0, 0);
+
+    public new ExtensionObject<ICommandContextItem> Model { get; } = new(contextItem);
+
+    public bool IsCritical { get; private set; }
+
+    public KeyChord? RequestedShortcut { get; private set; }
+
+    public bool HasRequestedShortcut => RequestedShortcut != null && (RequestedShortcut.Value != nullKeyChord);
+
+    public override void InitializeProperties()
+    {
+        if (IsInitialized)
+        {
+            return;
+        }
+
+        base.InitializeProperties();
+
+        var contextItem = Model.Unsafe;
+        if (contextItem == null)
+        {
+            return; // throw?
+        }
+
+        IsCritical = contextItem.IsCritical;
+
+        // I actually don't think this will ever actually be null, because
+        // KeyChord is a struct, which isn't nullable in WinRT
+        if (contextItem.RequestedShortcut != null)
+        {
+            RequestedShortcut = new(
+                contextItem.RequestedShortcut.Modifiers,
+                contextItem.RequestedShortcut.Vkey,
+                contextItem.RequestedShortcut.ScanCode);
+        }
+    }
+}