fix: Allow Shadowed Class Methods to Modify State Properties

[Devu-trenser]

Context

We need to extend BasicStatsCalculator to customize it for annotation use cases. Currently state is declared as private, which prevents extension and reuse of its internal state in the derived annotation-specific stats calculator.

This change updates state from private to protected to allow subclasses to directly access and build on top of it.

Changes & Results

• Change the visibility of the state field in BasicStatsCalculator from private to protected.

1. Before: the state property is inaccessible when extending the class for annotation custom stats calculators.
2. After: subclasses for annotation use can access and extend state directly.

Testing

Checklist

PR

• My Pull Request title is descriptive, accurate and follows the
  semantic-release format and guidelines.

Code

• [] My code has been well-documented (function documentation, inline comments,
  etc.)

Public Documentation Updates

• [] The documentation page has been updated as necessary for any public API
  additions or removals.

Tested Environment

• [] "OS:
• [] "Node version:
• [] "Browser: