This PR brings best practices mentioned to me on other prs and adds them
to the existing builtin tests.
Note to reviewers: I put this up in two commits because the clang-format
changes is making it hard to tell what actually changed.
use the first commit to check for correctness.
We previously made an implmenetation error when adding `half` overloads
for HLSL library functionalitly. The `half` type is always defined in
HLSL and `half` intrinsics should not be conditionally included.
When native 16-bit types are disabled `half` is a unique 32-bit float
type with lesser promotion rank than `float`.
Fixes#81049
