fix(kernel/normalizer): cache problems

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(kernel/replace_fn): non-recursive replace_fn

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(kernel/normalizer): avoid unnecessary creation of closures for n-ary functions

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