RetrievalLanes

Shared, key-agnostic retrieval-lane bookkeeping. Used by every poll-per-frame retriever that has a local cache in front of a remote source — the image earth.worldwind.render.RenderResourceCache (keyed by ImageSource) and the gridded-coverage earth.worldwind.globe.elevation.coverage.AbstractTiledElevationCoverage (keyed by tile Long).

Splits retrievals into a remote lane (anything fetched from a remote server) and a local lane (in-bundle resources, local files, and cache-only reads), so a slow remote fetch can never occupy a slot a local or cached read needs. The piece that makes the separation actually hold is cacheChecked: once a source's cache-only read misses, it is recorded so its cache read is NOT re-issued on every subsequent frame while it waits for a remote slot. Without that, a congested remote lane indirectly saturates the local lane with repeating cache-miss reads and starves genuine local resources.

The element type K is the retrieval's identity key (an ImageSource, a tile Long, …); it must have value-correct equals/hashCode since membership drives dedup and the lane budgets.

Not thread-safe: callers reserve/release from a single retrieval scope (the main scope on every platform), matching how the elevation and image stacks already drive retrieval.