[OpenACC] unify reduction and private-like init region recipes

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
(#135698, #137869) but did not get propagated to reductions, even
though they essentially do the same thing.

To mitigate this descrepency 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: Scott Manley

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> &);