Rename is_stop_never_possible to is_stop_ever_possible

The usage of this query quite often ends up needing to be negated which ends up with a double negative (not is stop never possible) instead of the positive form (is stop ever possible).

eg.
```
if constexpr (!is_stop_never_possible_v) {
// handle possibility of stop being requested
}
```

Inverting this and using the positive form would allow this code to read better:
```
if constexpr (is_stop_ever_possible_v) {
// handle possibility of stop being requested.
}
```