review and tidy Primitives.hs

`Primitives.hs` contains many things that are either needed but not really "true" primitives, or are relics from previous iterations and no longer required.

As far as I'm aware the only real fundamentally required primitives are:

- `word`
- the yul primops

We should review the set of primitives in `Primitives.hs` and:

1. remove the ones we don't need
2. consider extracting the remaining constructs into a `prelude.solc`

Start by reviewing Primitives.hs and cataloguing which definitions are required, especially word and the Yul primops, versus relics from earlier iterations. Then assess whether the remaining constructs belong in a prelude.solc. Done means the primitive set has been reviewed, unnecessary definitions are removed, and any extraction decision is documented or implemented.

Written by the indexing model from the issue text.