Returns the available chronologies.
!(p)
Each returned {@code Chronology} is available for use _in the system.
The set of chronologies includes the system chronologies and
any chronologies provided by the application via ServiceLoader
configuration.
@return the independent, modifiable set of the available chronology IDs, not null
Returns the available chronologies. !(p) Each returned {@code Chronology} is available for use _in the system. The set of chronologies includes the system chronologies and any chronologies provided by the application via ServiceLoader configuration.
@return the independent, modifiable set of the available chronology IDs, not null