Add reverse parameter for overflow direction control

[tddang-linagora]

Adds a new reverse parameter to OverflowView and OverflowView.flexible that allows overflow to occur from the start (left/top) instead of the end (right/bottom).

Features:

• Reverse mode trims from left (horizontal) or top (vertical)
• Overflow indicator appears at the start in reverse mode
• Works with both fixed and flexible layout modes
• Supports spacing in reverse mode

Performance:

• Optimized reverse layout to O(k) complexity for fixed mode
• Optimized reverse layout to O(n) complexity for flexible mode
• Eliminated O(n²) operations from initial implementation

Tests:

• Added comprehensive test coverage for reverse functionality
• All existing tests continue to pass

Bump version to 0.6.0