CmdPal: Add context commands for pinning nested commands (#45673)

_targets #45572_

This change allows our contact menu factory to actually create and add
additional context menu commands for pinning commands to the top level.
Now for any command provider built with the latest SDK that return
subcommands with an ID, we will add additional context menu commands
that allows you to pin that command to the top level.

<img width="540" height="181" alt="image"
src="https://github.com/user-attachments/assets/6c2cfe3c-4143-44d1-9308-bfc71db4c842"
/>
<img width="729" height="317" alt="image"
src="https://github.com/user-attachments/assets/4ff75c9f-1f35-4c1e-a03e-6fab5cbab423"
/>

related to https://github.com/microsoft/PowerToys/issues/45191
related to https://github.com/microsoft/PowerToys/issues/45201


This PR notably does not remove pinning from the apps extension. I
thought that made sense to do as a follow-up PR for the sake of
reviewability.

--- 

description from #45676 which was merged into this

Removes the code that the apps provider was using to support pinning
apps to the top level list of commands. Now the all apps provider just
uses the global support for pinning commands to the top level.

This does have the side effect of removing the separation of pinned apps
from unpinned apps on the All Apps page. However, we all pretty much
agree that wasn't a particularly widely used feature, and it's safe to
remove.

With this, we can finally call this issue done 🎉
closes https://github.com/microsoft/PowerToys/issues/45191

src/modules/cmdpal/Tests/Microsoft.CmdPal.Ext.Apps.UnitTests/AllAppsPageTests.cs

@@ -73,25 +73,4 @@ public class AllAppsPageTests : AppsTestBase
         Assert.IsTrue(items.Any(i => i.Title == "Notepad"));
         Assert.IsTrue(items.Any(i => i.Title == "Calculator"));
     }
-
-    [TestMethod]
-    public async Task AllAppsPage_GetPinnedApps_ReturnsEmptyWhenNoAppsArePinned()
-    {
-        // Arrange
-        var mockCache = new MockAppCache();
-        var app = TestDataHelper.CreateTestWin32Program("TestApp", "C:\\TestApp.exe");
-        mockCache.AddWin32Program(app);
-
-        var page = new AllAppsPage(mockCache);
-
-        // Wait a bit for initialization to complete
-        await Task.Delay(100);
-
-        // Act
-        var pinnedApps = page.GetPinnedApps();
-
-        // Assert
-        Assert.IsNotNull(pinnedApps);
-        Assert.AreEqual(0, pinnedApps.Length);
-    }
 }