refactor: collecting inlines for subjects

Instead of checking intersections of inline elements yourself before
adding an inline element, the new class `InlineElementCollector`
prevents intersections internally.

Additionally the inline elements are sorted by the new class, so it's no
longer necessary to do this after adding the inline elements.

src/Models/Commit.cs

@@ -121,6 +121,6 @@ namespace SourceGit.Models
     public class CommitFullMessage
     {
         public string Message { get; set; } = string.Empty;
-        public List<InlineElement> Inlines { get; set; } = [];
+        public InlineElementCollector Inlines { get; set; } = [];
     }
 }