Unified: Fix bad join in derivedStoreReadStep

Before
```
Pipeline standard for StaticNameBinding::derivedStoreReadStep/2#42234dff@fc4c9y3a was evaluated in 14 iterations totaling 10484ms (delta sizes total: 108052).
           5330410   ~0%    {3} r1 = JOIN `StaticNameBinding::TrackNamespace::track/1#cff0849d#reorder_1_0#prev_delta` WITH `StaticNameBinding::readStep/3#d06f28c6` ON FIRST 1 OUTPUT Lhs.1, Rhs.1, Rhs.2
              2567   ~0%    {2}    | JOIN WITH `StaticNameBinding::NamespaceNode.getMember/1#62056d4e#prev` ON FIRST 2 OUTPUT Lhs.2, Rhs.2
                            {2}    | REWRITE WITH TEST InOut.1 != InOut.0
              2567   ~1%    {2}    | SCAN OUTPUT In.1, In.0

            811176   ~0%    {3} r2 = SCAN `StaticNameBinding::NamespaceNode.getMember/1#62056d4e#prev_delta` OUTPUT In.1, In.0, In.2
        3703647034   ~1%    {4}    | JOIN WITH `StaticNameBinding::readStep/3#d06f28c6_102#join_rhs` ON FIRST 1 OUTPUT Rhs.1, Rhs.2, Lhs.1, Lhs.2
                            {4}    | REWRITE WITH TEST InOut.3 != InOut.1
        3703647034   ~0%    {4}    | SCAN OUTPUT In.0, In.2, In.1, In.3
            105485   ~0%    {2}    | JOIN WITH `StaticNameBinding::TrackNamespace::track/1#cff0849d#reorder_1_0#prev` ON FIRST 2 OUTPUT Lhs.3, Lhs.2

            108052   ~1%    {2} r3 = r1 UNION r2
            108052   ~1%    {2}    | AND NOT `StaticNameBinding::derivedStoreReadStep/2#42234dff#prev`(FIRST 2)
                            return r3
```

After
```
Pipeline standard for StaticNameBinding::derivedStoreReadStep/2#42234dff@7738dy18 was evaluated in 14 iterations totaling 42ms (delta sizes total: 108052).
        5330410   ~0%    {3} r1 = JOIN `StaticNameBinding::TrackNamespace::track/1#cff0849d#reorder_1_0#prev_delta` WITH `StaticNameBinding::readStep/3#d06f28c6` ON FIRST 1 OUTPUT Lhs.1, Rhs.1, Rhs.2
           2567   ~0%    {2}    | JOIN WITH `StaticNameBinding::NamespaceNode.getMember/1#62056d4e#prev` ON FIRST 2 OUTPUT Lhs.2, Rhs.2
                         {2}    | REWRITE WITH TEST InOut.1 != InOut.0
           2567   ~1%    {2}    | SCAN OUTPUT In.1, In.0

         811176   ~4%    {3} r2 = SCAN `StaticNameBinding::NamespaceNode.getMember/1#62056d4e#prev_delta` OUTPUT In.0, In.2, In.1
        5362528   ~0%    {3}    | JOIN WITH `StaticNameBinding::TrackNamespace::track/1#cff0849d#prev` ON FIRST 1 OUTPUT Rhs.1, Lhs.2, Lhs.1
         105485   ~0%    {2}    | JOIN WITH `StaticNameBinding::readStep/3#d06f28c6` ON FIRST 2 OUTPUT Lhs.2, Rhs.2
         105485   ~0%    {2}    | REWRITE WITH TEST InOut.0 != InOut.1

         108052   ~1%    {2} r3 = r1 UNION r2
         108052   ~1%    {2}    | AND NOT `StaticNameBinding::derivedStoreReadStep/2#42234dff#prev`(FIRST 2)
                         return r3
```

Author: hvitved

unified/ql/lib/codeql/unified/internal/StaticNameBinding.qll

@@ -341,8 +341,8 @@ module Track<TrackInputSig Input> {
 pragma[nomagic]
 private predicate derivedStoreReadStep(NameBindingNode node1, NameBindingNode node2) {
   exists(NamespaceNode namespace, string name |
-    node1 = namespace.getMember(name) and // getMember() combines a store step with subsequent inheritance steps
-    readStep(namespace.ref(), name, node2) and
+    node1 = namespace.getMember(pragma[only_bind_into](name)) and // getMember() combines a store step with subsequent inheritance steps
+    readStep(namespace.ref(), pragma[only_bind_into](name), node2) and
     node1 != node2
   )
 }