internal/rosa: pass stage alongside state

This cleans up many function signatures.

Signed-off-by: Ophestra <cat@gensokyo.uk>

cmd/mbf/internal/pkgserver/index.go

@@ -61,7 +61,7 @@ func (index *packageIndex) populate(report *rosa.Report) (err error) {
 	index.names = make(map[string]*metadata)
 	ir := pkg.NewIR()
 	for i, handle := range handles {
-		a, version := rosa.Native().Load(rosa.Std, handle)
+		a, version := rosa.Native().Std().MustLoad(handle)
 		m := metadata{
 			handle: handle,