[llvm] [DirectX][NFC] Change all DXIL TableGen tokens to CamelCase (PR #80714)

[Chris B via llvm-commits]

llvm-beanz wrote:

> I do not have commit access to `llvm-project` repo. May I request one of the approvers / reviewers to help by pushing the changes? Thanks!

Let's let the buildkite build finish just for posterity, then I'm happy to merge this.

https://github.com/llvm/llvm-project/pull/80714