swift234

[SILCombine] Use the opened archetype instead of reading the type from self

The opened archetype already has metatypes stripped off.

The problem was in code that tried to propagate the type from open_existentials
in static existential calls.

  %0 = metatype thick ClientSocket.Type
  %1 = init_existential_metatype %0 : thick ClientSocket.Type, thick Socket.Type
  %2 = open_existential_metatype %1 : thick Socket.Type to thick (@opened(...) Socket).Type
  %3 = witness_method opened(...) Socket, #Socket.newWithConfig!1, %2
  try_apply %3<@opened(...) Socket>(%2)

We would read the type of '%2' which is a metatype of '@open(...)' in the
substitution replacement code comparing it to the subsitution which is just
'@open(...)'. We already computed the archetype earlier so just use that
instead.

SR-811
rdar://24825970