[clang] [llvm] [HLSL] Move `normalize` implementation to header files (PR #216228)

[Kaitlin Peng via cfe-commits]

kmpeng wrote:

There is a `copysign` lowering bug that is causing the `normalize` offload-test-suite tests to fail. Moving this PR to draft while I fix that bug first.

https://github.com/llvm/llvm-project/pull/216228