Fix LINQ extension methods conversion to C#

[GrahamTheCoder]

Fixes issue where LINQ extension methods are incorrectly replaced with static Enumerable methods when converted from VB to C# (Issue #1149). This occurred because non-generic extension methods (like Sum or Max on int enumerables) were mistakenly bypassing a guard clause and expanding into full static method invocations during the VB syntax expansion step. The C# simplifier was subsequently failing to reduce them back.

By updating the VbNameExpander guard clause to cover all extension methods and reduced extension methods, the idiomatic fluent syntax is successfully preserved.

Included unit test verified against numeric collections Select().Sum(), OrderBy().Max(), Select().Count(), etc.

---

PR created automatically by Jules for task 17340425955327495994 started by @GrahamTheCoder

--

Updates VbNameExpander to correctly bypass syntax expansion for all extension methods (both generic and reduced, such as .Sum() over numeric collections). Previously, non-generic extension methods were expanded to static calls (e.g. Enumerable.Sum(...)), which the C# simplifier phase couldn't contract back to fluent syntax, leading to erroneous or uncompilable C# output.

Renames IsOriginalSymbolGenericMethod to IsOriginalSymbolGenericOrExtensionMethod to reflect its behavior of handling IsExtensionMethod and MethodKind.ReducedExtension.

Includes a new reproducing unit test LinqExtensionMethodReproTests to ensure continued functionality.