fix(frontends/lean): distribute '@' over choice

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(library/logic/connectives): make dependence prop <- eq <- basic
fix(frontends/lean/server): compilation warning

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(tests/lean/run/class_coe): adjust test to reflect library changes

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