C#: Support 'WithElement'.

Author: michaelnebel

csharp/ql/lib/semmle/code/csharp/dataflow/internal/FlowSummaryImplSpecific.qll

@@ -165,6 +165,8 @@ SummaryComponent interpretComponentSpecific(AccessPathToken c) {
   or
   c = "WithoutElement" and result = SummaryComponent::withoutContent(any(ElementContent ec))
   or
+  c = "WithElement" and result = SummaryComponent::withContent(any(ElementContent ec))
+  or
   // Qualified names may contain commas,such as in `Tuple<,>`, so get the entire argument list
   // rather than an individual argument.
   exists(Field f |
@@ -203,6 +205,8 @@ string getComponentSpecificCsv(SummaryComponent sc) {
   or
   exists(Content c | sc = TWithoutContentSummaryComponent(c) and result = "WithoutElement")
   or
+  exists(Content c | sc = TWithContentSummaryComponent(c) and result = "WithElement")
+  or
   exists(ReturnKind rk |
     sc = TReturnSummaryComponent(rk) and
     result = "ReturnValue[" + rk + "]" and