ref #26144
The C backend must not use `sfNeverRaises` to remove exception checks
from
virtual method calls. The flag describes only the selected base method
body,
while a vtable override may raise a catchable exception.
This change makes `canRaiseDisp` conservative for `skMethod` symbols and
adds a
regression test covering an exception raised by a child method invoked
through a
base reference.
(cherry picked from commit 8cb406cd7a)
