feat: Adds GetMobilesInRangeByDistance for tracking skill improvements

[kamronbatman]

No description provided.

[Copilot]

Pull Request Overview

This PR introduces a new distance-based enumeration system for finding mobiles within a specified range, optimized for tracking skill improvements. The implementation provides efficient spatial querying by using sector-based enumeration with ring traversal patterns.

Key changes:

• Adds GetMobilesInRangeByDistance methods with multiple overloads for different coordinate input types
• Implements a custom enumerator that returns mobiles sorted by proximity using sector-based ring traversal
• Provides minimum distance calculation for optimal performance in skill tracking scenarios

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[Copilot]

The ref readonly field _linkList is not initialized in the constructor and will cause a compilation error. Ref fields must be assigned in constructors or field initializers.

[Copilot]

Assignment to a ref readonly field is not allowed outside of the constructor. This line will cause a compilation error.

Suggested change

	Mobile current = _current;
	var linkList = map.GetRealSector(_currentSectorX, _currentSectorY).Mobiles;
	_currentVersion = linkList.Version;
	current = linkList._first;