[llvm] [DAG] isKnownNeverZero - add ISD::SRA/SRL DemandedElts handling and tests (PR #183577)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon requested changes to this pull request.

Once #184140 land you can drop your test files and just regenerate known-never-zero.ll

https://github.com/llvm/llvm-project/pull/183577