C#: Add more tests to effective visibility

Author: tamasvajk

csharp/ql/test/library-tests/modifiers/Effectively.expected

@@ -24,3 +24,5 @@
 | Modifiers.cs:60:22:60:23 | I1 | public |
 | Modifiers.cs:62:14:62:15 | M1 | public |
 | Modifiers.cs:63:14:63:15 | M2 | public |
+| Modifiers.cs:68:14:68:15 | M1 | internal |
+| Modifiers.cs:71:18:71:19 | C2 | public |

csharp/ql/test/library-tests/modifiers/Modifiers.cs

@@ -62,4 +62,17 @@ public interface I1
         void M1();
         void M2() => throw null;
     }
+
+    internal interface I2
+    {
+        void M1() => throw null;
+    }
+
+    public class C2 : I2
+    {
+        void I2.M1() => throw null;
+
+        protected private void M2() { }
+        protected internal void M3() { }
+    }
 }

csharp/ql/test/library-tests/modifiers/Modifiers.expected

@@ -49,3 +49,12 @@
 | Modifiers.cs:62:14:62:15 | M1 | file://:0:0:0:0 | public |
 | Modifiers.cs:63:14:63:15 | M2 | file://:0:0:0:0 | public |
 | Modifiers.cs:63:14:63:15 | M2 | file://:0:0:0:0 | virtual |
+| Modifiers.cs:66:24:66:25 | I2 | file://:0:0:0:0 | internal |
+| Modifiers.cs:68:14:68:15 | M1 | file://:0:0:0:0 | public |
+| Modifiers.cs:68:14:68:15 | M1 | file://:0:0:0:0 | virtual |
+| Modifiers.cs:71:18:71:19 | C2 | file://:0:0:0:0 | public |
+| Modifiers.cs:73:17:73:18 | M1 | file://:0:0:0:0 | private |
+| Modifiers.cs:75:32:75:33 | M2 | file://:0:0:0:0 | private |
+| Modifiers.cs:75:32:75:33 | M2 | file://:0:0:0:0 | protected |
+| Modifiers.cs:76:33:76:34 | M3 | file://:0:0:0:0 | internal |
+| Modifiers.cs:76:33:76:34 | M3 | file://:0:0:0:0 | protected |