[CGObjC] Open cleanup scope before SaveAndRestore CurrentFuncletPad and push CatchRetScope early

Pushing the `CatchRetScope` early causes cleanups for catch parameters to be emitted in the basic block of the catch handler instead of the `catchret.dest` block. This is important because the latter is not part of the catchpad and this caused code truncations due to ARC PreISel intrinsics in WinEHPrepare.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D137939