CmdPal: Add option to choose default order for Terminal profiles (#41945)

## Summary of the Pull Request

This PR adds a new drop-down to the Windows Terminal extension settings
page that allows the user to choose the default sort order of profiles.
The available options are:
- Default (currently alphabetical, but may change in the future)
- Alphabetical
- Most recently used

It also extends the app data to store AppSettings, including a list of
up to 64 recently used profiles, stored as pairs of profile name and
terminal app ID.

Pictures? Pictures!

<img width="1821" height="1097" alt="image"
src="https://github.com/user-attachments/assets/c751dcbf-e638-4207-a3e4-6dd283c5239c"
/>

<img width="1694" height="521" alt="image"
src="https://github.com/user-attachments/assets/914c0498-98fa-4ed7-997d-f988253c923c"
/>

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## PR Checklist

- [x] Closes: #41430 
- [ ] **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/ext/Microsoft.CmdPal.Ext.WindowsTerminal/Helpers/AppSettingsManager.cs

@@ -12,8 +12,6 @@ using Microsoft.CommandPalette.Extensions.Toolkit;
 
 namespace Microsoft.CmdPal.Ext.WindowsTerminal.Helpers;
 
-#nullable enable
-
 public sealed class AppSettingsManager
 {
     private const string FileName = "appsettings.json";
@@ -42,7 +40,7 @@ public sealed class AppSettingsManager
             if (File.Exists(_filePath))
             {
                 var json = File.ReadAllText(_filePath);
-                var loaded = JsonSerializer.Deserialize(json, AppSettingsJsonContext.Default.AppSettings);
+                var loaded = JsonSerializer.Deserialize(json, AppSettingsJsonContext.Default.AppSettings!);
                 if (loaded is not null)
                 {
                     Current = loaded;
@@ -60,7 +58,7 @@ public sealed class AppSettingsManager
     {
         try
         {
-            var json = JsonSerializer.Serialize(Current, AppSettingsJsonContext.Default.AppSettings);
+            var json = JsonSerializer.Serialize(Current, AppSettingsJsonContext.Default.AppSettings!);
             File.WriteAllText(_filePath, json);
         }
         catch (Exception ex)