Python: Address review comments

Limits `inferredNonLoadExpressionContext`, and extends the new parser
tests to also contain the legacy test cases.

Author: tausbn

python/ql/lib/semmle/python/Exprs.qll

@@ -61,6 +61,7 @@ private predicate hasNonLoadExpressionContextSeed(Expr e, TContext context) {
 }
 
 private predicate inferredNonLoadExpressionContext(Expr e, TContext context) {
+  hasExpressionContext(e) and
   exists(Expr root |
     hasNonLoadExpressionContextSeed(root, context) and
     propagatesExpressionContext*(root, e)

python/ql/test/library-tests/expr-context-parity/new_parser.py

@@ -1,14 +1,56 @@
+import package
+import package.module as imported_module
+from package import member
+from package import other as imported_member
+
+
 type Alias[T, *Ts, **P] = tuple[T, *Ts]
 
 
+annotated: object = value
+plain = annotated
+first = second = plain
+(tuple_target, [list_target, *rest]) = values
+(walrus_target := plain)
+
+for (loop_item, *loop_rest) in iterable:
+    pass
+
+items = [item for item in iterable]
+
+with manager as (resource, *resources):
+    pass
+
+try:
+    pass
+except Exception as error:
+    pass
+
 match subject:
     case [head, *tail] as whole:
         pass
     case {"key": captured, **rest_mapping}:
         pass
 
-
 try:
     pass
 except* RuntimeError as group_error:
     pass
+
+del plain
+del object_value.attribute
+del sequence[index]
+del tuple_target, list_target
+
+
+def function(positional, default=value, *args, keyword_only, **kwargs):
+    positional += 1
+    object_value.attribute = positional
+    sequence[index] = positional
+    return positional, default, args, keyword_only, kwargs
+
+
+lambda_function = (
+    lambda positional, default=value, *args, keyword_only, **kwargs:
+        (positional, default, args, keyword_only, kwargs)
+)