tst_integration: add a reproducer for qtro_enum_signature() failure

Amends 515711c520975049fea242eb08c6036b831c9655 (picked to 6.12),
which fixed a bug in the function that caused it to fail when the
QMeatEnum::scope() contained a "2". The failure is silent, with no
warning, so picking back to all active non-ESM branches.

Since the fix was not picked further than 6.12 (yet), the 6.11
build needs a QEXPECT_FAIL.

Pick-to: 6.12 6.11 6.8
Change-Id: Iba72390ba13984cad26b93b642c3dd472f7c24ba
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>