feat(frontends/lean): add calc_subst, calc_refl, calc_trans commands for configuring calc-expressions

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(emacs): add new calc commands to lean emacs mode

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(frontends/lean/notation_cmd): add register_notation_cmds procedure

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(frontends/lean/notation_cmd): add register_notation_cmds procedure