Avoid use of type manager in extact->construct folding

[s-perron]

When dealing with structs the type manager merge two different structs
into a single entry if they have all of the same decorations and
element types. This is because they hash to the same value in the hash
table. This can cause problems if you need to get the id of a type from
the type manager because you could get either one. In this case, it
returns the wrong one.

The fix avoids using the type manager in one place. I have not
looked closely at other places the type manager is used to make
sure it is used safely everywhere.

Fixes #5624

[LukasBanana]

Hi, we ran into this issue yesterday and your fix helps us partially, but we had to make an amended to address the problem in our scenario:
We changed GetContainerType to GetContainerTypeId and return only the ID instead of the type instance, since you mentioned in #5624 that the type manager can get confused with isomorphic struct. CompositeInsertToCompositeConstruct will then use that ID for the call to BuildCompositeConstruct instead of using type_mgr->GetId(container_type) again:

uint32_t GetContainerTypeId(Instruction* inst) {
  assert(inst->opcode() == spv::Op::OpCompositeInsert);
  analysis::DefUseManager* def_use_manager = inst->context()->get_def_use_mgr();
  uint32_t container_type_id = GetElementType(
      inst->type_id(), inst->begin() + 4, inst->end() - 1, def_use_manager);
  return container_type_id;
}
...
bool CompositeInsertToCompositeConstruct(
    IRContext* context, Instruction* inst,
    const std::vector<const analysis::Constant*>&) {
  assert(inst->opcode() == spv::Op::OpCompositeInsert &&
         "Wrong opcode.  Should be OpCompositeInsert.");
  if (inst->NumInOperands() < 3) return false;

  analysis::TypeManager* type_mgr = context->get_type_mgr();
  std::map<uint32_t, uint32_t> values_inserted = GetInsertedValues(inst);
  const uint32_t container_type_id = GetContainerTypeId(inst);
  const analysis::Type* container_type = type_mgr->GetType(container_type_id);
  if (container_type == nullptr) {
    return false;
  }

  if (!DoInsertedValuesCoverEntireObject(container_type, values_inserted)) {
    return false;
  }

  Instruction* construct =
      BuildCompositeConstruct(container_type_id, values_inserted, inst);
  InsertConstructedObject(inst, construct);
  return true;
}

Please feel free to take this change if that works for you as it's usually a bit time consuming to come up with a smaller test case than just providing our large shaders.

UPDATE:
While my posted changes resolved an issue in our test case, there are still some other validation errors in our larger auto-generated shaders, so I can't fully confirm yet whether this one fixed the problem for us. Just as a heads-up that this should be taken with a grain of salt.

[Keenuts]

Thanks for the details, I missed the part where the types could be replaced only partially, hence causing issues. LGTM!