Fix ownership errors in semantic member accessor pullbacks:
- Getter pullbacks: emit copy value operation before storing value.
- Setter pullbacks: track loaded value as a temporary, to be destroyed.
Add tests covering trivial, non-trivial, and address-only properties.
Resolves SR-12778 and SR-12779.
Support differentiation of property wrapper wrapped value getters and setters.
Create new pullback generation code path for "semantic member accessors".
"Semantic member accessors" are attached to member properties that have a
corresponding tangent stored property in the parent `TangentVector` type.
These accessors have special-case pullback generation based on their semantic
behavior. Currently, only getters and setters are supported.
This special-case pullback generation is currently used for stored property
accessors and property wrapper wrapped value accessors. In the future, it can
also be used to support `@differentiable(useInTangentVector)` computed
properties: SR-12636.
User-defined accesors cannot use this code path because they may use custom
logic that does not semantically perform a member access.
Resolves SR-12639.
