WICKET-6774: rework of component state

[papegaaij]

State of a component is no longer stored as an array but using instances of ComponentState. These have a smaller memory footprint in most cases, are more efficient and the code is easier to read (I hope).

Note that a small change in behavior is introduced: behavior ids are only maintained for statefull behaviors. Ids can change for other behaviors, also when combined on the same component.

ComponentState still needs documentation, but first let's agree on this approach.