internal/rosa/package: migrate kernel

This introduces bindings for extra paths and KnownChecksum, and exposes a passthrough special case.

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

cmd/mbf/main.go

@@ -755,7 +755,7 @@ func main() {
 			"shell",
 			"Interactive shell in the specified Rosa OS environment",
 			func(args []string) error {
-				handles := make([]rosa.ArtifactH, len(args)+3)
+				handles := make([]rosa.ArtifactH, len(args), len(args)+3)
 				for i, arg := range args {
 					handles[i] = rosa.ArtifactH(unique.Make(arg))
 					if meta, _ := rosa.Native().Std().Load(handles[i]); meta == nil {