Add update hook for core primitives

[artalar]

Currently we have only one public method to hook an update of atom or action call - onUpdate from reatom/hooks. There are few DX problems with that:

1. onUpdate have two overloads for atom and action with different behaviour (callback parameters), it could be not obvious especially for an action, coz "update" and "action call" is not connected semantically.
2. onUpdate call made the whole graph hot and could produce memory leaks in rare cases (dynamic fabric on top of a shared state + forgetting about unsubscribe)
3. If you need to hook an update / call just for a log the extra import and neediness of it deletion is not handy. For example, you have an atom and want to log the state during debug - you should import and write onUpdate(anAtom, console.log), BUT after this line deletion you should fix imports too - extra work for a temporal debug.
4. There could be a rare cases when dependent update hooks just don't work (the first spy on an atom which was just changed...)
5. onUpdate is a super common feature and one of the common tools to build almost anything with Reatom, it is strange that this API stored in a different package.

The proposal: add the same hook to all atoms and actions of the core package.

export interface Atom<State = any> {
  __reatom: AtomProto<State>
  pipe: Pipe<this>

  onChange: (cb: (newState: State, prevState: State) => void) => Unsubscribe
}

export interface Action<Params extends any[] = any[], Payload = any>
  extends Atom<Array<{ params: Params; payload: Payload }>> {
  (ctx: Ctx, ...params: Params): Payload

  onCall: (cb: (payload: Payload, params: Params) => void) => Unsubscribe
}

The overhead would be only around 0.1KB!

[BANOnotIT]

Action inherit onChange. What semantic will be if I do someAction.onChange((...args) => console.log(args))?

[artalar]

@BANOnotIT onChange will work the same as the internal update hook - the list of action calls during transaction includes the last one. We will not show this in any place of documentations, so I think it will be Ok.

[artalar]

released