Primary cache: don't denormalize splatted values

[teh-cmc]

The primary cache currently treats all components the same way, it's completely unaware of semantics.
In particular, it's completely unaware of splats.

A side-effect of this is that it will denormalize splatted values just like it will denormalize any other component: i.e. it stores the result of applying all the join and splat logic.
That means that if you have 1 points with a splatted color, those 1 million implicit colors will actually be materialized in the cache.