[llvm] [lit] Refactor available `ptxas` features (PR #154439)

[Justin Fargnoli via llvm-commits]

justinfargnoli wrote:

> I'd also lean towards using () or {} to represent these (i.e. ptxas(sm_90), ptxas(isa-8.4)) but that is more a matter of personal taste so if you or others disagree I'm happy to leave as is.

It looks like `lit` doesn't like the use of `()`, `{}`, or `<>`, so I went back to using `-`. 

https://github.com/llvm/llvm-project/pull/154439