Expect a jstring on the va_list, and implicitly construct a QString from
that.
As a drive-by, allow native methods to take parameters by reference, and
move implementation details into a Detail namespace.
Add test coverage.
Change-Id: I31214938ccaea3f4d539b432e29d12434dd98377
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Petri Virkkunen <petri.virkkunen@qt.io>
Reviewed-by: Assam Boudjelthia <assam.boudjelthia@qt.io>