fix where type promotion
Fixes #73298
I don't know whether `where` kernel actually supports type promotion, nor am I in the mood to find out, so it's manual type promotion.
Edit: nah, i can't tell TI to "promote to common dtype" because of bool condition, so manual type promotion is our only option.
I'll see what tests start failing and fix.
Uses some parts from #62084
Pull Request resolved: https://github.com/pytorch/pytorch/pull/76691
Approved by: https://github.com/mruberry
