xso-proc: add support for parsing attributes into Strings

This is bare-bones and is missing many features which we intend to add
in future commits, such as parsing from attributes whose names differ
from the field names and parsing into non-String types.

xso-proc/src/structs.rs

@@ -96,7 +96,7 @@ impl StructDef {
             .inner
             .make_from_events_statemachine(
                 &state_ty_ident,
-                &target_ty_ident.clone().into(),
+                &Path::from(target_ty_ident.clone()).into(),
                 "Struct",
             )?
             .with_augmented_init(|init| {