Python: Move Python 3.15 data-flow tests to a separate file

We won't be able to run these tests until Python 3.15 is actually out
(and our CI is using it), so it seemed easiest to just put them in their
own test directory.

Author: tausbn

python/ql/test/library-tests/dataflow/coverage-pep798/NormalDataflowTest.expected

@@ -0,0 +1,2 @@
+missingAnnotationOnSink
+testFailures

python/ql/test/library-tests/dataflow/coverage-pep798/NormalDataflowTest.ql

@@ -0,0 +1,2 @@
+import python
+import utils.test.dataflow.NormalDataflowTest

python/ql/test/library-tests/dataflow/coverage-pep798/test.py

@@ -0,0 +1,25 @@
+# PEP 798: Unpacking in comprehensions.
+# These desugar to `yield from`, so flow depends on yield-from support.
+
+def test_star_list_comp():
+    l = [[SOURCE]]
+    flat = [*x for x in l]
+    SINK(flat[0]) # $ MISSING:flow="SOURCE, l:-2 -> flat[0]"
+
+
+def test_star_set_comp():
+    l = [[SOURCE]]
+    flat = {*x for x in l}
+    SINK(flat.pop()) # $ MISSING:flow="SOURCE, l:-2 -> flat.pop()"
+
+
+def test_star_genexp():
+    l = [[SOURCE]]
+    g = (*x for x in l)
+    SINK(next(g)) # $ MISSING:flow="SOURCE, l:-2 -> next()"
+
+
+def test_star_dictcomp():
+    l = [{"key": SOURCE}]
+    merged = {**d for d in l}
+    SINK(merged["key"]) # $ MISSING:flow="SOURCE, l:-2 -> merged[..]"

python/ql/test/library-tests/dataflow/coverage/test.py

@@ -257,32 +257,6 @@ def test_yield_from():
     SINK(next(g)) # $ MISSING:flow="SOURCE, l:-1 -> next()"
 
 
-# PEP 798: Unpacking in comprehensions.
-# These desugar to `yield from`, so flow depends on yield-from support (see above).
-def test_star_list_comp():
-    l = [[SOURCE]]
-    flat = [*x for x in l]
-    SINK(flat[0]) # $ MISSING:flow="SOURCE, l:-2 -> flat[0]"
-
-
-def test_star_set_comp():
-    l = [[SOURCE]]
-    flat = {*x for x in l}
-    SINK(flat.pop()) # $ MISSING:flow="SOURCE, l:-2 -> flat.pop()"
-
-
-def test_star_genexp():
-    l = [[SOURCE]]
-    g = (*x for x in l)
-    SINK(next(g)) # $ MISSING:flow="SOURCE, l:-2 -> next()"
-
-
-def test_star_dictcomp():
-    l = [{"key": SOURCE}]
-    merged = {**d for d in l}
-    SINK(merged["key"]) # $ MISSING:flow="SOURCE, l:-2 -> merged[..]"
-
-
 # a statement rather than an expression, but related to generators
 def test_for():
     for x in gen(SOURCE):