Normalizes the time-zone ID, returning a {@code ZoneOffset} where possible.
!(p)
The returns a normalized {@code ZoneId} that can be used _in place of this ID.
The result will have {@code ZoneRules} equivalent to those returned by this object,
however the ID returned by {@code getId()} may be different.
!(p)
The normalization checks if the rules of this {@code ZoneId} have a fixed offset.
If they do, then the {@code ZoneOffset} equal to that offset is returned.
Otherwise {@code this} is returned.
Normalizes the time-zone ID, returning a {@code ZoneOffset} where possible. !(p) The returns a normalized {@code ZoneId} that can be used _in place of this ID. The result will have {@code ZoneRules} equivalent to those returned by this object, however the ID returned by {@code getId()} may be different. !(p) The normalization checks if the rules of this {@code ZoneId} have a fixed offset. If they do, then the {@code ZoneOffset} equal to that offset is returned. Otherwise {@code this} is returned.
@return the time-zone unique ID, not null