[llvm] [HLSL] Refactoring DXILABI.h to not depend on scope printer (PR #153840)

[Damyan Pepper via llvm-commits]

damyanp wrote:

@llvm-beanz - this is in response to https://github.com/llvm/llvm-project/pull/152229#discussion_r2278528672.  

Since this change is moving around existing to_underlying things rather than introducing new ones, woudl it be ok to get this in (thus fixing the 2% build time increase) and then prioritize landing #151032 (and making sure that the cases in this PR are addressed in that one as well)?

@joaosaffran - it would be good if the PR description more directly explained the motivation for this change without having to read through issues and links to comments on PRs.

https://github.com/llvm/llvm-project/pull/153840