Remove TargetMarkerFunction

It was only used by TransitiveBaseTraversalFunction, to which I moved
the error handling code that was previously in TargetMarkerFunction.

We see significantly faster deps() queries in some cases (~20%).

PiperOrigin-RevId: 247399011
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/TransitiveTraversalFunctionTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/TransitiveTraversalFunctionTest.java
index 9ca9b5d..5072eea 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/TransitiveTraversalFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/TransitiveTraversalFunctionTest.java
@@ -60,7 +60,7 @@
     TransitiveTraversalFunction function =
         new TransitiveTraversalFunction() {
           @Override
-          LoadTargetResults loadTarget(Environment env, Label label) {
+          TargetAndErrorIfAny loadTarget(Environment env, Label label) {
             return targetAndErrorIfAny;
           }
         };
@@ -69,7 +69,6 @@
     GroupedListHelper<SkyKey> helper = new GroupedListHelper<>();
     SkyKey fakeDep1 = function.getKey(Label.parseAbsolute("//foo:bar", ImmutableMap.of()));
     SkyKey fakeDep2 = function.getKey(Label.parseAbsolute("//foo:baz", ImmutableMap.of()));
-    helper.add(TargetMarkerValue.key(label));
     helper.add(PackageValue.key(label.getPackageIdentifier()));
     helper.startGroup();
     // Note that these targets don't actually exist in the package we created initially. It doesn't
@@ -84,7 +83,7 @@
     SkyFunction.Environment mockEnv = Mockito.mock(SkyFunction.Environment.class);
     when(mockEnv.getTemporaryDirectDeps()).thenReturn(groupedList);
     when(mockEnv.getValuesOrThrow(
-            groupedList.get(2), NoSuchPackageException.class, NoSuchTargetException.class))
+            groupedList.get(1), NoSuchPackageException.class, NoSuchTargetException.class))
         .thenAnswer(
             (invocationOnMock) -> {
               wasOptimizationUsed.set(true);
@@ -116,7 +115,7 @@
     TransitiveTraversalFunction function =
         new TransitiveTraversalFunction() {
           @Override
-          LoadTargetResults loadTarget(Environment env, Label label) {
+          TargetAndErrorIfAny loadTarget(Environment env, Label label) {
             return targetAndErrorIfAny;
           }
         };
@@ -168,7 +167,7 @@
     TransitiveTraversalFunction function =
         new TransitiveTraversalFunction() {
           @Override
-          LoadTargetResults loadTarget(Environment env, Label label) {
+          TargetAndErrorIfAny loadTarget(Environment env, Label label) {
             return targetAndErrorIfAny;
           }
         };
@@ -181,10 +180,9 @@
         .thenReturn(ImmutableMap.of(dep, makeException("bad bar")));
     when(mockEnv.valuesMissing()).thenReturn(false);
 
-    assertThat(
-            ((TransitiveTraversalValue) function.compute(function.getKey(label), mockEnv))
-                .getErrorMessage())
-        .isEqualTo("self error is long and last");
+    TransitiveTraversalValue transitiveTraversalValue =
+        (TransitiveTraversalValue) function.compute(function.getKey(label), mockEnv);
+    assertThat(transitiveTraversalValue.getErrorMessage()).isEqualTo("self error is long and last");
   }
 
   private static ValueOrException2<NoSuchPackageException, NoSuchTargetException> makeException(