feat(api): improve subscriptions management in Observables and RegionObservers

[S-furi]

This PR aims at improving current Observable subscriptions management. Firstly, the Disposable pattern is enforced by making Node and Actionable adhere to such contract. Moreover, taking inspiration from LiveData in androidx, the concept of Lifecycle and owners of such lifecycle are introduced.
With this paradigm, automatic dependency cleanup on multiple observables is performed just by using the bridge Observble<T>.bindTo(LifeCycleOwner, (T) -> Unit), which let us avoid zombie callbacks and automatic disposal of resources when observers lifecycle is over without making the observable holding strong references to them.
This pattern also helps in avoiding the usage of weak references, which are (1) not very performant in the form of WeakHashMap (2) hard to use them in a multi platform environment (still no support for native and Js WeakMap is not iterable).
With this new method, we reduce the chances to leak subscribers while making developers avoid to explicitly track every subscription and making sure to dispose them when observers references are lost. Moreover, components lifecycle management could be further bound to the simulation lifecycle in future developments, making Lifecycle events even more meaningful (e.g. ready state on simulation initial configuration, no observers emissions; then started state when simulation starts, start observers emission; then destroyed state when simulation stops, remove every subscription to observers).

Finally this PR tries to better handle RegionObservers in environment, by managing their lifecycle by means of reference counting. While they provide lazy mechanisms (a region observer starts emitting only when observers are registered), when the observers count reach zero, the region is removed from regions' caches avoiding regions leaking. Still regions could leak resources if developers poorly handle subscriptions by not properly disposing them, however the above Lifecycle approach could help.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 61.53%. Comparing base (5ee3457) to head (ba4f2f3).

Additional details and impacted files

@@                   Coverage Diff                   @@
##             feat/reactive-engine    #5101   +/-   ##
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  Coverage                   61.53%   61.53%           
  Complexity                     14       14           
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  Files                           2        2           
  Lines                          78       78           
  Branches                        4        4           
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  Hits                           48       48           
  Misses                         24       24           
  Partials                        6        6           

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