fix(library/util): is_eq was returning true for partially applied terms
fix(library/util): is_eq was returning true for partially applied terms

This commit also cleanups many of the is_* predicates

Kha/lean,leanprover-community/lean,johoelzl/lean,leanprover/lean,dselsam/lean,digama0/lean,avigad/lean,dselsam/lean,johoelzl/lean,digama0/lean,leanprover/lean,leanprover/lean,leanprover/lean,leanprover-community/lean,dselsam/lean,dselsam/lean,Kha/lean,avigad/lean,johoelzl/lean,johoelzl/lean,leodemoura/lean,leodemoura/lean,rlewis1988/lean,rlewis1988/lean,leodemoura/lean,johoelzl/lean,fpvandoorn/lean,leanprover/lean,rlewis1988/lean,fgdorais/lean,digama0/lean,digama0/lean,leodemoura/lean,avigad/lean,Kha/lean,leanprover-community/lean,fgdorais/lean,digama0/lean,leanprover-community/lean,rlewis1988/lean,dselsam/lean,Kha/lean,fgdorais/lean,fgdorais/lean,rlewis1988/lean,fpvandoorn/lean,leanprover-community/lean,leodemoura/lean,fgdorais/lean,fpvandoorn/lean,avigad/lean,Kha/lean,fpvandoorn/lean,johoelzl/lean,leanprover/lean,avigad/lean,Kha/lean,rlewis1988/lean,avigad/lean,digama0/lean,leodemoura/lean,fpvandoorn/lean,fgdorais/lean,fpvandoorn/lean,dselsam/lean,leanprover-community/lean