Clean diagnostic rules

Move the following diagnostics into static readonly fields: GD0101, GD0102, GD0103, GD0104, GD0105, GD0106, GD0107, GD0201, GD0202, GD0203, GD0301, GD0302, GD0303, GD0401, GD0402.

To be more consistent, the titles for the following diagnostics were modified: GD0101, GD0105, GD0106, GD0302, GD0303, GD0401, GD0402. A subsequent update of the documentation repo is needed.

Tests for the following diagnostics were created: GD0201, GD0202, GD0203.

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

@@ -4,4 +4,15 @@ public partial class EventSignals : GodotObject
 {
     [Signal]
     public delegate void MySignalEventHandler(string str, int num);
+
+    private struct MyStruct { }
+
+    [Signal]
+    private delegate void {|GD0201:MyInvalidSignal|}();
+
+    [Signal]
+    private delegate void MyInvalidParameterTypeSignalEventHandler(MyStruct {|GD0202:myStruct|});
+
+    [Signal]
+    private delegate MyStruct {|GD0203:MyInvalidReturnTypeSignalEventHandler|}();
 }

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators.Tests/TestData/Sources/GlobalClass.GD0401.cs

@@ -15,8 +15,8 @@ public partial class CustomGlobalClass2 : Node
 }
 
 // This raises a GD0401 diagnostic error: global classes must inherit from GodotObject
-{|GD0401:[GlobalClass]
-public partial class CustomGlobalClass3 
+[GlobalClass]
+public partial class {|GD0401:CustomGlobalClass3|}
 {
 
-}|}
+}

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators.Tests/TestData/Sources/GlobalClass.GD0402.cs

@@ -8,8 +8,8 @@ public partial class CustomGlobalClass : GodotObject
 }
 
 // This raises a GD0402 diagnostic error: global classes can't have any generic type parameter
-{|GD0402:[GlobalClass]
-public partial class CustomGlobalClass<T> : GodotObject
+[GlobalClass]
+public partial class {|GD0402:CustomGlobalClass|}<T> : GodotObject
 {
 
-}|}
+}