test(tests/lean/run): add nested let-expr test
test(tests/lean/run): add nested let-expr test

Signed-off-by: Leonardo de Moura <7610bae85f2b530654cc716772f1fe653373e892@microsoft.com>

leodemoura/lean,fgdorais/lean,sp3ctum/lean,levnach/lean,avigad/lean,c-cube/lean,leanprover-community/lean,eigengrau/lean,rlewis1988/lean,leanprover/lean,javra/lean,dselsam/lean,sp3ctum/lean,levnach/lean,UlrikBuchholtz/lean,fgdorais/lean,UlrikBuchholtz/lean,avigad/lean,soonhokong/lean-windows,fpvandoorn/lean2,javra/lean,digama0/lean,rlewis1988/lean,soonhokong/lean-windows,c-cube/lean,avigad/lean,soonhokong/lean-osx,htzh/lean,digama0/lean,dselsam/lean,htzh/lean,soonhokong/lean-osx,levnach/lean,UlrikBuchholtz/lean,leodemoura/lean,digama0/lean,leanprover-community/lean,fpvandoorn/lean2,fgdorais/lean,soonhokong/lean,Kha/lean,leodemoura/lean,johoelzl/lean,c-cube/lean,eigengrau/lean,javra/lean,soonhokong/lean-windows,leanprover-community/lean,soonhokong/lean-osx,leodemoura/lean,leanprover/lean,soonhokong/lean,fpvandoorn/lean2,dselsam/lean,fpvandoorn/lean,javra/lean,levnach/lean,johoelzl/lean,johoelzl/lean,levnach/lean,htzh/lean,soonhokong/lean-osx,Kha/lean,leanprover/lean,soonhokong/lean,leanprover-community/lean,fgdorais/lean,fpvandoorn/lean,leodemoura/lean,javra/lean,sp3ctum/lean,soonhokong/lean-windows,fgdorais/lean,Kha/lean,sp3ctum/lean,fpvandoorn/lean,leanprover/lean,Kha/lean,leanprover-community/lean,digama0/lean,Kha/lean,rlewis1988/lean,rlewis1988/lean,Kha/lean,eigengrau/lean,fpvandoorn/lean2,sp3ctum/lean,UlrikBuchholtz/lean,eigengrau/lean,fpvandoorn/lean2,dselsam/lean,johoelzl/lean,htzh/lean,soonhokong/lean,htzh/lean,avigad/lean,c-cube/lean,fpvandoorn/lean,avigad/lean,johoelzl/lean,johoelzl/lean,digama0/lean,dselsam/lean,fgdorais/lean,c-cube/lean,fpvandoorn/lean,UlrikBuchholtz/lean,digama0/lean,dselsam/lean,rlewis1988/lean,leanprover-community/lean,soonhokong/lean-windows,soonhokong/lean,soonhokong/lean-osx,fpvandoorn/lean,leanprover/lean,rlewis1988/lean,eigengrau/lean,leodemoura/lean,avigad/lean,leanprover/lean