Improvements

• Java 21 is used for building and using the library.
• #878: Allow Virtual-Threads evaluating the fitness function. Must be enabled when creating an Engine (see code snippet below), the previous behaviour has been preserverd.

final Engine<DoubleGene, Double> engine = Engine.builder(ff)
	.fitnessExecutor(BatchExecutor.ofVirtualThreads())
	.build();

• #880: Replace code examples in Javadoc with JEP 413.
• #886: Improve CharStore sort.
• #894: New genetic operators: ShiftMutator, ShuffleMutator and UniformOrderBasedCrossover.
• #895: Improve default RandomGenerator selection. The used RandomGenerator is selected in the following order:
  1. Check if the io.jenetics.util.defaultRandomGenerator start parameter is set. If so, take this generator.
  2. Check if the L64X256MixRandom generator is available. If so, take this generator.
  3. Find the best available random generator according to the RandomGeneratorFactory.stateBits() value.
  4. Use the Random generator if no best generator can be found. This generator is guaranteed to be available on every platform.