[llvm] Deprecate Type::getPointerTo() (#113331)

`llvm::Type::getPointerTo()` is no longer needed with opaque pointers in LLVM.
It may rather confuse new contributors to think that LLVM has typed pointers.

Author: JOE1994

llvm/include/llvm/IR/Type.h

@@ -472,8 +472,9 @@ class Type {
   static Type *getWasm_FuncrefTy(LLVMContext &C);
 
   /// Return a pointer to the current type. This is equivalent to
-  /// PointerType::get(Foo, AddrSpace).
+  /// PointerType::get(Ctx, AddrSpace).
   /// TODO: Remove this after opaque pointer transition is complete.
+  LLVM_DEPRECATED("Use PointerType::get instead", "PointerType::get")
   PointerType *getPointerTo(unsigned AddrSpace = 0) const;
 
 private: