[CVP] Canonicalize signed relational comparisons of scalar integers to...

[CVP] Canonicalize signed relational comparisons of scalar integers to unsigned comparison predicates

Now that the reasoning was added to ConstantRange in D90924,
this replicates IndVars variant of this transform (D111836)
in a pass that uses value range reasoning for the transform.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D112895