[EmitC] [203455] Inconsistent handling of emitc.lvalue function arguments between mlir-opt and mlir-translate

mlir-opt accepts func.func arguments of type !emitc.lvalue<...>, but mlir-translate --mlir-to-cpp rejects the same IR.

Reproducer

```mlir
func.func @member_access(
%arg0: !emitc.lvalue>) {

%0 = "emitc.member"(%arg0) {member = "a"}
: (!emitc.lvalue>)
-> !emitc.lvalue

return
}
```

Commands

`mlir-opt test.mlir`

succeeds.

`mlir-translate --mlir-to-cpp test.mlir`

fails with

`error: 'func.func' op cannot emit lvalue type as argument type`

Expected behavior

Either

func.func verification should reject !emitc.lvalue argument types, making mlir-opt consistent with the translator,

or

the C++ translator should support emitting !emitc.lvalue function arguments.

Run the supplied reproducer with mlir-opt and mlir-translate --mlir-to-cpp, then trace how EmitC lvalue function arguments are verified and translated at those entry points. Done when the selected behavior is implemented and both commands handle the reproducer consistently.

Written by the indexing model from the issue text.