Fix ExtensionMethod target typing for poly expressions in Eclipse

[z-xhh]

Summary

This change fixes Eclipse @ExtensionMethod resolution when an argument is a poly expression that already carries an overly broad resolved type.

In the failing case, a call like:

order.canRefund(Collections.emptyList())

could be treated as passing List<Object> instead of List<RefundOrderDto>. That caused extension method resolution to fail before the call could be rewritten to the static extension method form.

What Changed

• Prefer PolyTypeBinding for poly-expression arguments in the Eclipse extension-method resolution path, instead of only doing so when resolvedType is null.
• Add a regression test covering extension-method target typing with an empty generic list argument.
• Use Collections.emptyList() in the regression test so the case stays valid on the ECJ test path and isolates the actual inference issue.

Why This Matters

Without this change, valid extension-method calls can be rejected in Eclipse/JDT because argument typing is finalized too early and loses the target type required by the extension method signature.

Repro

Given an extension method like:

public static boolean canRefund(OrderDto order, List<RefundOrderDto> refunds)

a call such as:

order.canRefund(Collections.emptyList())

could fail in Eclipse/JDT with an error equivalent to:

The method canRefund(OrderDto, List<RefundOrderDto>) is not applicable for the arguments (OrderDto, List<Object>)

Validation

• dist test.eclipse-202503
• test.compile