refactor(kernel/builtin): Bool type does not need to be a semantic attachment

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(kernel/builtin): emove mk_bin_rop and mk_bin_lop to library

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(frontends/lean): add Alias command

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(library/arith): replace Nat, Int, Real with simple variable decls instead of semantic attachments

This commit also fixes bugs in the Alias command.

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