Support sampling of antenna terms at unique time, feed and antenna, rather than per row #268
Description
Within the FUSED RIME, the beam is sampled twice per row, and there is a non-trivial degree of computation involved: https://github.com/ska-sa/codex-africanus/blob/174645637b39ea037a7b557e29cdebd55ba0146c/africanus/experimental/rime/fused/terms/cube_dde.py#L149-L295
The performant solution would to evaluate antenna terms per unique, time, feed and antenna, multiply them together and cache the results for use within the RIME onion.
Originally posted by @sjperkins in #265 (comment)