[mlir][sparse] Adding a new overload of `getOpaquePointerType`

[wrengr]

Summary

(This will be used in future patches, but is split off for easier reviewing)

mlir/lib/Dialect/SparseTensor/Transforms/CodegenUtils.h

 /// Creates a `CallOp` to the function reference returned by `getFunc()` in
 /// the builder's module.
 func::CallOp createFuncCall(OpBuilder &builder, Location loc, StringRef name,
                             TypeRange resultType, ValueRange operands,
                             EmitCInterface emitCInterface);
 
 /// Returns the equivalent of `void*` for opaque arguments to the
 /// execution engine.
-Type getOpaquePointerType(OpBuilder &builder);
+Type getOpaquePointerType(MLIRContext *ctx);
+Type getOpaquePointerType(Builder &builder);
 
 /// Generates an uninitialized temporary buffer of the given size and
 /// type, but returns it as type `memref<? x $tp>` (rather than as type
 /// `memref<$sz x $tp>`).
 Value genAlloca(OpBuilder &builder, Location loc, Value sz, Type tp);
 
 /// Generates an uninitialized temporary buffer of the given size and
 /// type, and returns it as type `memref<? x $tp>` (staticShape=false) or

mlir/lib/Dialect/SparseTensor/Transforms/CodegenUtils.cpp

func::CallOp mlir::sparse_tensor::createFuncCall(
     OpBuilder &builder, Location loc, StringRef name, TypeRange resultType,
     ValueRange operands, EmitCInterface emitCInterface) {
   auto module = builder.getBlock()->getParentOp()->getParentOfType<ModuleOp>();
   FlatSymbolRefAttr fn =
       getFunc(module, name, resultType, operands, emitCInterface);
   return builder.create<func::CallOp>(loc, resultType, fn, operands);
 }
 
-Type mlir::sparse_tensor::getOpaquePointerType(OpBuilder &builder) {
-  return LLVM::LLVMPointerType::get(builder.getI8Type());
+Type mlir::sparse_tensor::getOpaquePointerType(MLIRContext *ctx) {
+  return LLVM::LLVMPointerType::get(IntegerType::get(ctx, 8));
+}
+
+Type mlir::sparse_tensor::getOpaquePointerType(Builder &builder) {
+  return getOpaquePointerType(builder.getContext());
 }
 
 Value mlir::sparse_tensor::genAlloca(OpBuilder &builder, Location loc,
                                      unsigned sz, Type tp, bool staticShape) {
   if (staticShape) {
     auto memTp = MemRefType::get({sz}, tp);
     return builder.create<memref::AllocaOp>(loc, memTp);
   }