provide analyser corresponding to the GD0001 and GD0002, add ClassPartialModifierAnalyzerFix, and tests

Co-authored-by: Raul Santos <raulsntos@gmail.com>
Co-authored-by: A Thousand Ships <96648715+AThousandShips@users.noreply.github.com>

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators.Tests/TestData/Sources/ClassPartialModifier.GD0001.cs

@@ -0,0 +1,6 @@
+using Godot;
+
+public class {|GD0001:ClassPartialModifier|} : Node
+{
+    
+}

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators.Tests/TestData/Sources/OuterClassPartialModifierAnalyzer.GD0002.cs

@@ -0,0 +1,11 @@
+using Godot;
+
+public class {|GD0002:OuterOuterClassPartialModifierAnalyzer|}
+{
+    public class {|GD0002:OuterClassPartialModifierAnalyzer|}
+    {
+        // MyNode is contained in a non-partial type so the source generators
+        // can't enhance this type to work with Godot.
+        public partial class MyNode : Node { }
+    }
+}