Add tests and fix exports diagnostics

- Add tests for the following diagnostics: GD0101, GD0102, GD0103, GD0104, GD0105, GD0106, GD0107.
- Fix GD0101 not being reported any more (was filtering static classes before reporting).
- Fix GD0107 not preventing `Node` members from being exported from not-`Node` types.

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators.Tests/TestData/Sources/ExportDiagnostics_GD0101.cs

@@ -0,0 +1,10 @@
+using Godot;
+
+public partial class ExportDiagnostics_GD0101 : Node
+{
+    [Export]
+    public static string {|GD0101:StaticField|};
+
+    [Export]
+    public static int {|GD0101:StaticProperty|} { get; set; }
+}

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators.Tests/TestData/Sources/ExportDiagnostics_GD0102.cs

@@ -0,0 +1,12 @@
+using Godot;
+
+public partial class ExportDiagnostics_GD0102 : Node
+{
+    public struct MyStruct { }
+
+    [Export]
+    public MyStruct {|GD0102:StructField|};
+
+    [Export]
+    public MyStruct {|GD0102:StructProperty|} { get; set; }
+}

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators.Tests/TestData/Sources/ExportDiagnostics_GD0103.cs

@@ -0,0 +1,10 @@
+using Godot;
+
+public partial class ExportDiagnostics_GD0103 : Node
+{
+    [Export]
+    public readonly string {|GD0103:ReadOnlyField|};
+
+    [Export]
+    public string {|GD0103:ReadOnlyProperty|} { get; }
+}

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators.Tests/TestData/Sources/ExportDiagnostics_GD0104.cs

@@ -0,0 +1,7 @@
+using Godot;
+
+public partial class ExportDiagnostics_GD0104 : Node
+{
+    [Export]
+    public string {|GD0104:WriteOnlyProperty|} { set { } }
+}

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators.Tests/TestData/Sources/ExportDiagnostics_GD0105.cs

@@ -0,0 +1,12 @@
+using System;
+using Godot;
+
+public partial class ExportDiagnostics_GD0105 : Node
+{
+    [Export]
+    public int {|GD0105:this|}[int index]
+    {
+        get { return index; }
+        set { }
+    }
+}

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators.Tests/TestData/Sources/ExportDiagnostics_GD0106.cs

@@ -0,0 +1,18 @@
+using Godot;
+
+public interface MyInterface
+{
+    public int MyProperty { get; set; }
+}
+
+public partial class ExportDiagnostics_GD0106_OK : Node, MyInterface
+{
+    [Export]
+    public int MyProperty { get; set; }
+}
+
+public partial class ExportDiagnostics_GD0106_KO : Node, MyInterface
+{
+    [Export]
+    int MyInterface.{|GD0106:MyProperty|} { get; set; }
+}

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators.Tests/TestData/Sources/ExportDiagnostics_GD0107.cs

@@ -0,0 +1,19 @@
+using Godot;
+
+public partial class ExportDiagnostics_GD0107_OK : Node
+{
+    [Export]
+    public Node NodeField;
+
+    [Export]
+    public Node NodeProperty { get; set; }
+}
+
+public partial class ExportDiagnostics_GD0107_KO : Resource
+{
+    [Export]
+    public Node {|GD0107:NodeField|};
+
+    [Export]
+    public Node {|GD0107:NodeProperty|} { get; set; }
+}