feat(kernel): add infer implicit, and use it to infer implicit arguments of inductive datatype eliminators, and tag whether parameters should be implicit or not in introduction rules in the module inductive_cmd

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(frontends/lean/inductive_cmd): redesign inductive datatype elaboration, use the new elaborator, and use simpler algorithm to infer the resulting universe

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