Add ComputedTracker to each function that returns something

[Benno]

🐛 Bug report

🤖 Current Behavior

Currently functions like exists(), is(), .. can't get autodetected by the Computed Class since we don't track it.

🎯 Expected behavior

Track each class that doesn't return this, since it can influence the Computed Value

📄 Reproducible example

💡 Suggested solution(s)

add ComputedTracker.tracked(this.observer);

[Benno]

In theory, it should already track the stuff in case of exists() or is()
since the function internally calls this.value which then calls the ComputedTracker.

 return !this.isPlaceholder && this.computeExistsMethod(this.value);
//                                                                                             |  (calls this.value)
// --------------------------------------------------------------

[Benno]

Not tracked methods:

• getGroupCount() (not trackable)
• getSelectorCount() (not trackable)
• getPublicValue() (intentional because internal method)
• getPersistableValue() (inentional because internal method)

the rest should now be trackable