[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:

> The code changes can be viewed in PR #164946. I've created a new PR as requested by @topperc in one of the comments in the code change PR. Do let me know if this is not desired.

This isn't precommitting tests as requested. This is 2 PRs which are unmergeable since both will just fail tests. Precommit is adding *new* tests prior to the patch, not splitting the post-patch test updates 

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