Shortcut rangechecking for small values

[matthiasgoergens]

At the moment every value we rangecheck from eg the CPU table goes through a two step process:

1. We look it up from the CPU table into the (u32) rangecheck table.
2. Then we look up four values from the (u32) rangecheck table into the u8 rangecheck table.

That's a total of five lookups, and 4 extra values we need to commit to.

For small values, we can shortcut that process: directly look up from the CPU table into the u8 rangecheck table.

As far as the CPU is concerned, any value to be rangechecked would be non-deterministically looked up in one of the rangecheck tables.

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We would need to rangecheck to see whether this buys us anything, because the ability to do multiplicities in the u32 rangecheck table might already gives us most of the benefit.