Merge pull request #15426 from michaelnebel/csharp/collectionexpressions

C# 12: Support for collection expressions.

Author: michaelnebel

csharp/downgrades/fc9c7ab844ab055b97222a97e895b4bf2e1f8f4e/expressions.ql

@@ -0,0 +1,13 @@
+class Expression extends @expr {
+  string toString() { none() }
+}
+
+class TypeOrRef extends @type_or_ref {
+  string toString() { none() }
+}
+
+from Expression e, int k, int kind, TypeOrRef t
+where
+  expressions(e, k, t) and
+  if k = [136, 137] then kind = 106 else kind = k
+select e, kind, t