Adding Lock to RecentCommandsManager (#40507)

According to Issue #40447 Without the Lock in RecentCommandsManager we
get Exception:
Collection was modified; enumeration operation may not execute.

It indicated that while GetCommandHistoryWeight was enumerating History,
another method (likely AddHistoryItem) modified it at the same time.
Since List is not thread-safe, simultaneous read+write can break it.

## Summary of the Pull Request

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## PR Checklist

- [ ] **Closes:** #xxx
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Unit Tests all pass, Manually Tested as Well
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
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I've checked that in this project we use the new .NET 9 locking instead
of object locking and implemented it according to rest of the locks
## Detailed Description of the Pull Request / Additional comments

I've Manually tested it and also made sure that all the unit test pass
## Validation Steps Performed

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/RecentCommandsManager.cs

@@ -12,11 +12,15 @@ public partial class RecentCommandsManager : ObservableObject
     [JsonInclude]
     internal List<HistoryItem> History { get; set; } = [];
 
+    private readonly Lock _lock = new();
+
     public RecentCommandsManager()
     {
     }
 
     public int GetCommandHistoryWeight(string commandId)
+    {
+        lock (_lock)
         {
             var entry = History
             .Index()
@@ -48,8 +52,11 @@ public partial class RecentCommandsManager : ObservableObject
 
             return 0;
         }
+    }
 
     public void AddHistoryItem(string commandId)
+    {
+        lock (_lock)
         {
             var entry = History
             .Where(item => item.CommandId == commandId)
@@ -72,3 +79,4 @@ public partial class RecentCommandsManager : ObservableObject
             }
         }
     }
+}