Optimize LightList copies

[8Keep]

Needs my jmh harness PR in jMonkeyEngine#2778

Summary

• avoid copying and clearing unused retained LightList backing capacity
• use bulk copy/fill paths for unfiltered world light-list updates
• keep the retained sort buffer sized to active lights instead of backing-array capacity
• add focused LightList regression tests for removal ordering, update ordering/filtering, and sorting after retained capacity

Benchmark Results

JMH results from the jme3-core benchmark harness, lower is better:

Before -> After

• removeFromFront, 256 lights: 0.317 us/op -> 0.036 us/op
• removeFromMiddle, 256 lights: 0.172 us/op -> 0.031 us/op
• updateFromLocalAndParent, 256 lights: 0.738 us/op -> 0.195 us/op
• sortTransformChanged, 256 lights, retained x1024: 94.191 us/op -> 25.909 us/op

Testing

• ./gradlew :jme3-core:test --tests com.jme3.light.LightListTest :jme3-core:benchmarkClasses