feat(library/vm/vm): improve vm_obj pretty printer
feat(library/vm/vm): improve vm_obj pretty printer

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