StgToByteCode: Fix overly-broad handling of Addr# literals

Previously we assumed that all unlifted types were Addr# but this isn't true. As noted in #25638, unlifted nullary data constructor workers can also appear at the top-level and are obviously not of type Addr#.

Note that there is more work to be done to properly handle unlifted data constructors (especially nullary; see #25636). However, this is a small step in the right direction.

Fixes #25641 (closed).