This prevented `std::vector<std::string>` from being auto-conformed to `CxxRandomAccessCollection`.
If an iterator type is templated, and does not have an explicit instantiation via a typedef or a using-decl, its specialization will not have an owning Clang module. Make sure we treat it as a part of the Clang module that owns the template decl.
rdar://112762768 / resolves https://github.com/apple/swift/issues/67410
Adds tests for using std-vector and some other interesting types.
This patch fixes four mis conceptions that the compiler was previously making:
1. Implicit destructors have no side effects. (Yes, this means we were not cleaning up some objects.)
2. Implicit destructors have bodies. (Technically they do, but the body doesn't include CallExprs that they make when lowered to IR.)
3. Functions other than methods can be uninstantiated templates.
4. Uninstantiated templates may have executable code. (I.e., we can never take the fast path.)
And makes sure that we visit the destructor of any VarDecl (including parameters).
