Add a missing trimArityType
Fix a buglet in arity-finding.
I also moved some Notes from GHC.Core.Opt.Simplify.Utils to GHC.Core.Opt.Arity, where they more properly belong.
Fix a buglet in arity-finding.
I also moved some Notes from GHC.Core.Opt.Simplify.Utils to GHC.Core.Opt.Arity, where they more properly belong.