Feat: Added reactive SortedSet

[hmoog]

Description of change

This PR introduces a reactive SortedSet, which extends the capabilities of the Set to derive a perception of weight and order for its elements.

We expose the information through the following additional API endpoints:

// SortedSet is a reactive Set implementation that allows consumers to subscribe to its changes 
// and that keeps a sorted perception of its elements.
type SortedSet[ElementType comparable] interface {
    // Set imports the methods of the Set interface.
    Set[ElementType]

    // Ascending returns a slice of all elements of the set in ascending order.
    Ascending() []ElementType

    // Descending returns a slice of all elements of the set in descending order.
    Descending() []ElementType

    // HeaviestElement returns the element with the heaviest weight.
    HeaviestElement() ReadableVariable[ElementType]

    // LightestElement returns the element with the lightest weight.
    LightestElement() ReadableVariable[ElementType]
}

Type of change

• Enhancement (a non-breaking change which adds functionality)

Change checklist

• [x] My code follows the contribution guidelines for this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes