struct Rav1dIntraPredDspContext::cfl_ac: Make an EnumMap over Rav1dPixelLayoutSubSampled

[kkysen]

I'll do the same for the other array fields, but I need to make the enums for those first; this one already exists from before.

[rinon]

This change itself looks fine.

However, what does this actually enable with regards to safety improvements? Was this actually blocking anything or is this a readability improvement? We need to focus on only what is blocking memory safety improvements.

[kkysen]

However, what does this actually enable with regards to safety improvements? Was this actually blocking anything or is this a readability improvement? We need to focus on only what is blocking memory safety improvements.

This was to remove the bounds check, since enums are restricted to only their values. Since we're now focusing on getting everything safe first before ensuring we don't have perf regressions, I'll hold off on these types of changes until we get everything safe. The improvement in readability/type safety is nice here, but was more of a secondary concern.