Change signatures to DerivedArtifact, and get Labels from non-Artifact sources when possible.

In tests, try to get artifacts directly from the actual configured target, rather than creating fresh ones.

This change should be a prod functional no-op, just changing signatures. Split out from the follow-up to reduce the diff.

PiperOrigin-RevId: 250527865
diff --git a/src/test/java/com/google/devtools/build/lib/analysis/AspectTest.java b/src/test/java/com/google/devtools/build/lib/analysis/AspectTest.java
index 2b80208..cf4b1a3 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/AspectTest.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/AspectTest.java
@@ -536,7 +536,7 @@
     update();
 
     ConfiguredTarget a = getConfiguredTarget("//a:a");
-    NestedSet<Artifact> extraActionArtifacts =
+    NestedSet<Artifact.DerivedArtifact> extraActionArtifacts =
         a.getProvider(ExtraActionArtifactsProvider.class).getTransitiveExtraActionArtifacts();
     for (Artifact artifact : extraActionArtifacts) {
       assertThat(artifact.getOwnerLabel()).isEqualTo(Label.create("@//a", "b"));