This PR slightly improves the types involved in creating boxed
declarations. Previously the type of
the vdecl used for the return was always `tobj` when returning a boxed
scalar. This is not the most
precise annotation we can give.
This PR exposes the definitions about `Int*`. The main reason is that
the `SInt` simprocs require many of them to be exposed. Furthermore,
`decide` now works with `Int*` operations. This fixes#10631.
This is mostly a refactoring that replaces other analyses with type
information, but due to the introduction of `tagged` it also has the
side effect of eliminating ref counting ops entirely for types that
always have a tagged scalar representation, e.g. `Unit`.
