Clean a bunch of C# warnings

- `[Obsolete]` tag generated in the middle of documentation comments
- Potential `null` values in generators
- Obsolete call to `GetEditorInterface()`
- We don't want `Godot.Collections.Array` to end with `Collection`
- A few culture specifications and use of `AsSpan` instead of `SubString` in `StringExtensions`
- Disable CA1716 in GodotSharp

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/Helper.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+
+namespace Godot.SourceGenerators
+{
+    public static class Helper
+    {
+        [Conditional("DEBUG")]
+        public static void ThrowIfNull([NotNull] object? value)
+        {
+            _ = value ?? throw new ArgumentNullException();
+        }
+    }
+}