[6.2][cxx-interop] Fix import virtual methods with rvalue ref params
Explanation: We generate forwarding calls for virutal methods. These forwarding
calls had a type error when the original parameter had an rvalue reference type.
In those scenarios we need to insert a static cast to make the type checker happy.
Issues: rdar://154969620
Original PRs: #83453
Risk: Low, narrow fix.
Testing: Added a compiler test.
Reviewers: @egorzhdan