Up until recently we were using wildcard re-exports for types moved to
`units` and `primitives`. We have decided against doing so in favour of
explicit re-exports.
Audit `units` and `primitives` using `git grep 'pub enum'` (and
`struct`) and explicitly re-export all types.
Remove all wildcards except for the re-exports from `opcodes`, there are
too many opcodes, explicitly re-exporting them does not aid clarity.
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