Fix VB to C# conversion for extension methods on properties passed by ref

* Generalize `HoistByRefDeclaration` in `ArgumentConverter` to accept `ExpressionSyntax`.
* Update `NameExpressionNodeVisitor` to correctly process extension method receiver ref-conversions, hoisting the receiver expression (e.g., properties) into a temporary variable when required by `ByRef`.
* Introduce `TestExtensionMethodRefPropertyAsync` to explicitly verify property ref assignments to extension methods generate a valid C# state.

Co-authored-by: GrahamTheCoder <2490482+GrahamTheCoder@users.noreply.github.com>

Author: google-labs-jules[bot]