Spatial (resolution-aware and context-aware) caching

Spatial, and likely temporal, caching needs to with based on storing cached data at different zoom levels, areas in space (forming a patchwork quilt of cache hit areas within surroundings of cache miss areas), and different times in the animation timeline. All this will be needed to make Cache nodes relation-aware to work with footprint data.

首先映射现有的 Cache 节点以及图形引擎中关系感知的 footprint 处理。定义缓存数据应如何随缩放级别、空间区域和动画时间而变化，然后记录测试，以证明 miss 周围存在拼接式的缓存命中，并且在时间线发生变化时能够正确失效。

由索引模型根据 Issue 内容生成。