[NFC][SCEV] Prepare `createNodeForSelectOrPHI()` for gaining additional strategy

Currently `createNodeForSelectOrPHI()` takes an Instruction,
and only works on the Cond that is an ICmpInst,
but that can be relaxed somewhat.

For now, simply rename the existing function,
and add a thin wrapper ontop that still does
the same thing as it used to.