TypeLowering: add Type.hasCustomDeinit

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• [NFC] TypeLowering: add CustomDeinit.
  Teach SIL type lowering to recursively track custom vs. default deinit status.

  Determine whether each type recursively only has default deinitialization. This
  includes any recursive deinitializers that may be invoked by releasing a
  reference held by this type.

  If a type only has default deinitialization, then the deinitializer cannot
  have any semantically-visible side effects. It cannot write to any memory

• SwiftCompilerSources bridge Type.hasCustomDeinit.

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@slavapestov Take a look at classifyTypeParameters.
012116e#diff-f225973f74fb5d01a20a43ffa69ab2ee1652880a40733d654d4c20bba3612879R2779

We need this for certain certain types (Array, Dictionary) that may only have a custom deinit when their generic parameters may have a custome deinit (hasConditionalDefaultDeinit() == true). So type lowering an Array<Element> requires checking the CustomDeinit flag on the Element type parameter.

I'm using an opaque abstraction pattern, guessing that it can't affect recursive type properties. But maybe this code should know how to extract the originalElementType from AbstractionPattern origType that corresponds to each generic parameter in the BoundGenericType, before calling getTypeLowering(origElementType, paramType,...)?

Here's the code:

    RecursiveProperties classifyTypeParameters(CanType type, TypeConverter &tc,
                                               TypeExpansionContext expansion) {
      RecursiveProperties props;
      if (auto bgt = dyn_cast<BoundGenericType>(type)) {
        for (auto paramType : bgt->getGenericArgs()) {
          // Use an opaque abstraction pattern for the element type because
          // abstraction does not apply to the generic parameter itself.
          AbstractionPattern origElementType = AbstractionPattern::getOpaque();
          auto &lowering = tc.getTypeLowering(origElementType, paramType,
                                              expansion);
          props.addSubobject(lowering.getRecursiveProperties());
        }
      }
      return props;
    }

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@swift-ci test

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@swift-ci test