feat(signal-slice): add "Updated" signal for action sources

[joshuamorony]

NOTE: This depends on #361 being merged, this is branched off of that feature

This is a replacement for the removal of the actionEffect API, instead it allows triggering side effects as a result of an actionSource emitting via a notifier/version signal (same general concept we used for createNotifier).

It adds a <actionSourceName>Updated signal for each action source e.g:

  state = signalSlice({
    initialState: this.initialState,
    actionSources: {
      load: (_state, $: Observable<void>) => $.pipe(
        switchMap(() => this.someService.load()),
        map(data => ({ someProperty: data })
      )
    }
  })

  effect(() => {
    // triggered when `load` emits/completes and on init
    console.log(state.loadUpdated())
  })

  effect(() => {
	if (state.loadUpdated()) {
	  // triggered ONLY when `load` emits/completes
	  // NOT on init
	}
  });

This is a much simpler API and avoids the typing issues (described in: #361)

[michael-small]

Sounds like a fair tradeoff to me. If the pattern of this PR and the base PR is to de-couple signalSlice from formal effect blocks, then having some sort distinction between other effect in a file unrelated to the slice and effect related to the slice is a nice tradeoff.

[eneajaho]

Hello @joshuamorony
Can you add the breaking change in the commit description if this is a breaking change?

[joshuamorony]

@eneajaho we ended up merging #361 and this is ready for review now (no breaking changes in this PR)

[eneajaho]

@joshuamorony can you rebase? Then I can merge

[joshuamorony]

@eneajaho done