perf(library/unifier): delay the instantiation of metavariables occurring in the types of local constants

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(shell/lean): rename multi-threading option to -j

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(library/unifier): bugs exposed by recent changes

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(kernel/find_fn): simplify find_fn module

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(kernel/for_each_fn): simplify module interface

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(kernel/replace_fn): bug in the cache

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
perf(kernel/for_each_fn): use cache stack trick at for_each_fn

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