[llvm] [hlsl] Pin hlsl-test-all resusable workflow to main branch (PR #122518)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

@llvm-beanz How is the runner setup? Is it physical hardware on a network with anything sensitive? A cloud VM somewhere? If it's trivial to nuke from orbit and can't touch anything anyone would care about, I think that changes the security posture versus if those things aren't true.

https://github.com/llvm/llvm-project/pull/122518