Fix C# CustomPathStateProblem compilation and enhance test with meaningful results

Co-authored-by: MichaelRFairhurst <1627771+MichaelRFairhurst@users.noreply.github.com>

Author: Copilot

csharp/src/qtil/csharp/graph/CustomPathStateProblem.qll

@@ -2,4 +2,4 @@ private import qtil.locations.CustomPathStateProblem
 private import qtil.csharp.locations.Locatable
 private import csharp
 // Import the C# specific configuration for making custom path state problems.
-import PathStateProblem<csharp::Location, CsharpLocatableConfig>
+import PathStateProblem<Location, CsharpLocatableConfig>

csharp/test/qtil/csharp/graph/CustomPathStateProblemTest.expected

@@ -1,3 +1,9 @@
 edges
+| test.cs:4:13:4:15 | mid | test.cs:3:13:3:15 | end |  |  |
+| test.cs:5:13:5:17 | start | test.cs:4:13:4:15 | mid |  |  |
 nodes
-#select
+| test.cs:3:13:3:15 | end | semmle.label | end |
+| test.cs:4:13:4:15 | mid | semmle.label | mid |
+| test.cs:5:13:5:17 | start | semmle.label | start |
+#select
+| test.cs:5:13:5:17 | start | test.cs:3:13:3:15 | end | Path from $@ to $@. | start | test.cs:5:13:5:17 | start | end | test.cs:3:13:3:15 | end |

csharp/test/qtil/csharp/graph/CustomPathStateProblemTest.ql

@@ -10,7 +10,7 @@ module CallGraphPathStateProblemConfig implements CustomPathStateProblemConfigSi
   predicate start(Node n, int depth) { n.getName() = "start" and depth = 0 }
 
   bindingset[depth]
-  predicate end(Node n, int depth) { n.getName() = "end" }
+  predicate end(Node n, int depth) { n.getName() = "end" and depth >= 0 }
 
   bindingset[depth1]
   bindingset[depth2]

csharp/test/qtil/csharp/graph/test.cs

@@ -1,11 +1,8 @@
 public class Test {
     void f1() {
-        int mid = 0;
-        int start = 0;
-        int end = 0;
+        int end = 42;
+        int mid = end;
+        int start = mid;
         int unrelated = 0;
-        start = mid;
-        start = unrelated;
-        mid = end;
     }
 }

ruby/test/qtil/ruby/graph/CustomPathStateProblemTest.ql

@@ -28,4 +28,5 @@ import CustomPathStateProblem<CallGraphPathStateProblemConfig>
 
 from Ast::VariableWriteAccess start, Ast::VariableWriteAccess end
 where problem(start, end)
-select start, end, "Path from $@ to $@.", start.getVariable().getName(), start, end.getVariable().getName(), end
+select start, end, "Path from $@ to $@.", start.getVariable().getName(), start,
+  end.getVariable().getName(), end