fix: optimize Set by using struct{} instead of bool for memory efficiency

[WolfieLeader]

Description

This PR optimizes the Set implementation by replacing the bool value with an empty struct (struct{}). This significantly reduces memory usage, especially for large data sets.

Motivation

The Set previously used a map[T]bool, where each value occupied at least one byte. Since the actual value in a Set is irrelevant (presence of a key implies membership), this value can be replaced with an empty struct (struct{}), which has zero memory allocation in Go.

This change enhances memory efficiency without affecting functionality or performance negatively.

Changes

• Replaced map[T]bool with map[T]struct{} for Set implementation.

Checklist

• Code compiles and passes tests.
• Implementation is idiomatic and conforms to Go best practices.
• Changes are isolated to a single logical unit.
• File naming and formatting follow repository guidelines.
• Added or updated tests as necessary.