C#: Add some tests for cs/linq/missed-all.

Author: michaelnebel

csharp/ql/test/query-tests/Linq/MissedAllOpportunity/MissedAllOpportunity.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Linq;
+using System.Collections.Generic;
+
+class MissedAllOpportunity
+{
+    public void M1(List<int> lst)
+    {
+        // BAD: Can be replaced with lst.All(e => e % 2 == 0)
+        var allEven = true;
+        foreach (int i in lst)
+        {
+            if (i % 2 != 0)
+            {
+                allEven = false;
+                break;
+            }
+        } // $ Alert
+    }
+
+    public void M2(NonEnumerableClass nec)
+    {
+        // GOOD: Linq can't be used here.
+        var allEven = true;
+        foreach (int i in nec)
+        {
+            if (i % 2 != 0)
+            {
+                allEven = false;
+                break;
+            }
+        }
+    }
+
+    public class NonEnumerableClass
+    {
+        public IEnumerator<int> GetEnumerator() => throw null;
+    }
+}

csharp/ql/test/query-tests/Linq/MissedAllOpportunity/MissedAllOpportunity.expected

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+| MissedAllOpportunity.cs:11:9:18:9 | foreach (... ... in ...) ... | This foreach loop looks as if it might be testing whether every sequence element satisfies a predicate - consider using '.All(...)'. |

csharp/ql/test/query-tests/Linq/MissedAllOpportunity/MissedAllOpportunity.qlref

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+query: Linq/MissedAllOpportunity.ql
+postprocess: utils/test/InlineExpectationsTestQuery.ql

csharp/ql/test/query-tests/Linq/MissedAllOpportunity/options

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+semmle-extractor-options: /nostdlib /noconfig
+semmle-extractor-options: --load-sources-from-project:${testdir}/../../../resources/stubs/_frameworks/Microsoft.NETCore.App/Microsoft.NETCore.App.csproj