Handle begin_apply in TempRVO

A tempobj passed to begin_apply instruction and cannot be modified by it
(is guaranteed and doesn't alias with other inout args) can be optimzed
away.

Author: meg-gupta

lib/SILOptimizer/Transforms/TempRValueElimination.cpp

@@ -171,6 +171,7 @@ bool TempRValueOptPass::collectLoads(
       return false;
      LLVM_FALLTHROUGH;
   case SILInstructionKind::ApplyInst:
+  case SILInstructionKind::BeginApplyInst:
   case SILInstructionKind::TryApplyInst: {
     ApplySite apply(user);