[llvm] [SelectionDAG] Add SelectionDAG::getTypeSize. NFC (PR #169764)

[Luke Lau via llvm-commits]

================
@@ -2117,13 +2102,24 @@ SDValue SelectionDAG::getVScale(const SDLoc &DL, EVT VT, APInt MulImm,
   return getNode(ISD::VSCALE, DL, VT, getConstant(MulImm, DL, VT));
 }
 
+template <typename Ty>
----------------
lukel97 wrote:

Added a comment in 5c13c4abc950dc5f6ade54dd76365ad8ba8016f8.

It's templated since it needs to work over both ElementType and TypeSize, both of which inherit from `details::FixedOrScalableQuantity<LeafTy, ScalarTy>`, but with different LeafTy and ScalarTys. 

https://github.com/llvm/llvm-project/pull/169764