Extract resolve_test_path from resolve_test_discovery

Summary: Just a little refactor to simplify the next diff

Reviewed By: cjhopman

Differential Revision: D92513345

fbshipit-source-id: 34b036bbd4a27274a980a01bfa9d155e54fcecf5

Author: Ian Childs

app/buck2_core/src/fs/buck_out_path.rs

@@ -398,6 +398,14 @@ impl BuckOutPathResolver {
     pub fn resolve_test_discovery(
         &self,
         label: &ConfiguredProvidersLabel,
+    ) -> buck2_error::Result<ProjectRelativePathBuf> {
+        self.resolve_test_path(&ForwardRelativePath::unchecked_new("test_discovery"), label)
+    }
+
+    fn resolve_test_path(
+        &self,
+        prefix: &ForwardRelativePath,
+        label: &ConfiguredProvidersLabel,
     ) -> buck2_error::Result<ProjectRelativePathBuf> {
         let path = match label.name() {
             ProvidersName::Default => "default".into(),
@@ -413,7 +421,7 @@ impl BuckOutPathResolver {
         };
         let path = ForwardRelativePath::unchecked_new(&path);
         self.prefixed_path_for_owner(
-            ForwardRelativePath::unchecked_new("test_discovery"),
+            prefix,
             &BaseDeferredKey::TargetLabel(label.target().dupe()),
             None,
             path,