[mlir] Fix CallOpInterface extraClassDeclaration to be fully namespace qualified (#81258)

`extraClassDeclaration` of `CallOpInterface` can be inherited by other
`OpInterfaces` into foreign namespaces, thus types must be fully
qualified to prevent compiler errors, for example:

    def MyCaller : OpInterface<"MyCaller", [CallOpInterface]> {
        let cppNamespace = "::MyNamespace";
    }