Build VisFlagsWeights on ChunkStore
Build VisFlagsWeights on ChunkStore

This uses the metadata in TelstateDataSource to construct a
VisFlagsWeights instance that connects to the relevant ChunkStore
(only RADOS for now). Wrap the resulting dask arrays to make them
appear like old-school LazyIndexers. The capture block ID + stream
detection is also missing for now (requires controller support),
so a manual override is mandatory.

ska-sa/katdal