[llvm] [DAG] Precommit test for PR #164946 - Update Tests SimplifyDemandedBits - ICMP_SLT(X,0) - only sign mask of X is required (PR #171030)

[Matt Arsenault via llvm-commits]

arsenm wrote:

Precommit tests would mean adding new tests, but this is just a bunch of changes in existing tests with no code changes?

> Resolves https://github.com/llvm/llvm-project/issues/164589

A test-only can't really resolve an issue? 

https://github.com/llvm/llvm-project/pull/171030