when note_and_explain_type_err is called during dyn-compatibility checking, the body_owner_def_id can be CRATE_DEF_ID because ObligationCause::dummy() uses it as a placeholder when there is no real body owner. calling generics_of on CRATE_DEF_ID caused an ICE because the crate root is a module and modules don't have generics. the fix guards all generics_of call sites by checking whether body_owner_def_id is CRATE_DEF_ID before attempting to look up generics, and skips the type parameter span labeling in that case.

i also added regression test with original ice reproduce

fixes #152335