Checks if the specified field is supported.
|the field to check, null returns false|
Implementations must check and handle all fields defined in
If the field is supported, then true must be returned, otherwise false must be returned.
If the field is not a
ChronoField, then the result of this method
is obtained by invoking
this as the argument.
Implementations must ensure that no observable state is altered when this
read-only method is invoked.