Fixes markup warnings (#6525)

* fixes: suppress warning  CS0659  Type overrides Object.Equals(object o) but does not override Object.GetHashCode()

* fixes: Warning CS0108 'AvaloniaXamlIlCompiler._configuration' hides inherited member 'XamlCompiler<IXamlILEmitter, XamlILNodeEmitResult>._configuration'. Use the new keyword if hiding was intended.

* fixes: Warning CS8765 Nullability of type of parameter 'obj' doesn't match overridden member.

src/Avalonia.Visuals/Vector.cs

@@ -175,7 +175,7 @@ namespace Avalonia
                    MathUtilities.AreClose(_y, other._y);
         }
 
-        public override bool Equals(object obj) => obj is Vector other && Equals(other);
+        public override bool Equals(object? obj) => obj is Vector other && Equals(other);
 
         public override int GetHashCode()
         {

src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/AvaloniaXamlIlCompiler.cs

@@ -14,7 +14,6 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions
 {
     class AvaloniaXamlIlCompiler : XamlILCompiler
     {
-        private readonly TransformerConfiguration _configuration;
         private readonly IXamlType _contextType;
         private readonly AvaloniaXamlIlDesignPropertiesTransformer _designTransformer;
         private readonly AvaloniaBindingExtensionTransformer _bindingTransformer;
@@ -22,8 +21,6 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions
         private AvaloniaXamlIlCompiler(TransformerConfiguration configuration, XamlLanguageEmitMappings<IXamlILEmitter, XamlILNodeEmitResult> emitMappings)
             : base(configuration, emitMappings, true)
         {
-            _configuration = configuration;
-
             void InsertAfter<T>(params IXamlAstTransformer[] t) 
                 => Transformers.InsertRange(Transformers.FindIndex(x => x is T) + 1, t);
 

src/Markup/Avalonia.Markup/Markup/Parsers/PropertyPathGrammar.cs

@@ -184,6 +184,9 @@ namespace Avalonia.Markup.Parsers
             
         }
 
+        // Don't need to override GetHashCode as the ISyntax objects will not be stored in a hash; the 
+        // only reason they have overridden Equals methods is for unit testing.
+#pragma warning disable CS0659 // Type overrides Object.Equals(object o) but does not override Object.GetHashCode()
         public class PropertySyntax : ISyntax
         {
             public string Name { get; set; } = string.Empty;
@@ -205,7 +208,7 @@ namespace Avalonia.Markup.Parsers
                    && other.TypeName == TypeName
                    && other.TypeNamespace == TypeNamespace;
         }
-        
+
         public class ChildTraversalSyntax : ISyntax
         {
             public static ChildTraversalSyntax Instance { get;  } = new ChildTraversalSyntax();
@@ -231,5 +234,6 @@ namespace Avalonia.Markup.Parsers
                    && other.TypeName == TypeName
                    && other.TypeNamespace == TypeNamespace;
         }
+#pragma warning restore CS0659 // Type overrides Object.Equals(object o) but does not override Object.GetHashCode()
     }
 }