[std::vec] Rename .pop_opt() to .pop(), drop the old .pop() behavior
[std::vec] Rename .shift_opt() to .shift(), drop the old .shift() behavior
[std::vec] Rename .remove_opt() to .remove(), drop the old .remove() behavior
[std::path] Rename .container_as_str_opt() to .container_as_str(), drop the old .container_as_str() behavior
[std::str] Rename from_utf8_opt() to from_utf8(), drop the old from_utf8() behavior
[std::str] Rename from_utf8_owned_opt() to from_utf8_owned(), drop the old from_utf8_owned() behavior
[std::str] Remove the now unused not_utf8 condition.