The `dx.dot2`, `dot3`, and `dot4` intrinsics exist purely to lower
`dx.fdot`, and they map exactly to the DXIL ops of the same name. Using
vectors for their arguments adds unnecessary complexity and causes us to
have vector operations that are not trivial to lower post-scalarizer.
Similarly, the `dx.dot2add` intrinsic is overly generic for something
that only needs to lower to a single `dot2AddHalf` DXIL op. Update its
signature to match the operation it lowers to.
Fixes#134569.
Line ending policies were changed in the parent, dccebddb3b80. To make
it easier to resolve downstream merge conflicts after line-ending
policies are adjusted this is a separate whitespace-only commit. If you
have merge conflicts as a result, you can simply `git add --renormalize
-u && git merge --continue` or `git add --renormalize -u && git rebase
--continue` - depending on your workflow.
