refactor(util/log_tree): use for_each
refactor(util/log_tree): use for_each

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