Function is_submodulite_exported

submodulite @msg/core is exported from @msg when - "@msg/core" is declared in 'export' - or "@msg/core" is declared in 'allow-internal' for current usage context - or usage context is @msg/channels, it can access @msg/core, because @msg is their lca if check_all_depth, checks are done for any chains, e.g. @parent/c1/c2/c3 — c3 from c2, c2 from c1, c1 from parent else, check is not only for child f