Add advanced set operations and polyfills to Set extension

Introduces polyfills for common set operations (union, difference, intersection, symmetricDifference, isSubsetOf, isSupersetOf, isDisjointFrom) on Set.prototype. Adds corresponding Scratch blocks for these operations, as well as improved builder functionality, set stringification with formatting options, and enhanced type conversion logic. Refactors internal logic to use new polyfills and improves toString and toJSON methods for SetType.

Author: DogeisCut