goose: add a test for imports across packages

Reviewed-by: Tuo Shan <shantuo@google.com>
Reviewed-by: Herbie Ong <herbie@google.com>

internal/goose/testdata/PkgImport/bar/bar.go

@@ -0,0 +1,8 @@
+package bar
+
+type Bar int
+
+//goose:provide Bar
+func ProvideBar() Bar {
+	return 1
+}