[OpenACC] unify reduction and private-like init region recipes (llvm#140652)

Between firstprivate, private and reduction init regions, the difference
is largely whether or not the temp that is created is initialized or
not. Some recent fixes were made to privatization (llvm#135698, llvm#137869) but
did not get propagated to reductions, even though they need to return
the yield the same things from their init regions.

To mitigate this discrepancy in the future, refactor the init region
recipes so they can be shared between the three recipe ops.

Also add "none" to the OpenACC_ReductionOperator enum for better error
checking.

Author: rscottmanley

flang/include/flang/Lower/OpenACC.h

@@ -85,7 +85,7 @@ void genOpenACCRoutineConstruct(
 
 /// Get a acc.private.recipe op for the given type or create it if it does not
 /// exist yet.
-mlir::acc::PrivateRecipeOp createOrGetPrivateRecipe(mlir::OpBuilder &,
+mlir::acc::PrivateRecipeOp createOrGetPrivateRecipe(fir::FirOpBuilder &,
                                                     llvm::StringRef,
                                                     mlir::Location, mlir::Type);
 
@@ -99,7 +99,7 @@ createOrGetReductionRecipe(fir::FirOpBuilder &, llvm::StringRef, mlir::Location,
 /// Get a acc.firstprivate.recipe op for the given type or create it if it does
 /// not exist yet.
 mlir::acc::FirstprivateRecipeOp
-createOrGetFirstprivateRecipe(mlir::OpBuilder &, llvm::StringRef,
+createOrGetFirstprivateRecipe(fir::FirOpBuilder &, llvm::StringRef,
                               mlir::Location, mlir::Type,
                               llvm::SmallVector<mlir::Value> &);