[CSClosure] Handle wrapped variables without explicit initializers
All variables without explicit initializers were considered to be
uninitialized which is incorrect because if a variable has a property
wrapper attached to it that wrapper needs its initializer type-checked,
for example:
```
@propertyWrapper
struct Wrapper {
var name: String
...
}
test {
@wrapper(name: "wrapper")
var v;
}
```
`v` gets initialized via a call to `Wrapper(name: "wrapper")`.
Resolves: rdar://91225620
(cherry picked from commit 869a413aae6b584b42987d61562620d126929b17)