Cover constructor, destructor, and local initializer side effects

Add static global objects with separately side-effecting constructors and destructors, and record the unused-local false positive for a side-effecting initializer.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: jketema

cpp/ql/test/query-tests/Best Practices/Unused Entities/UnusedLocals/UnusedLocals.expected

@@ -6,6 +6,7 @@
 | code2.cpp:64:7:64:8 | v3 | Variable v3 is not used. |
 | code2.cpp:108:11:108:12 | v2 | Variable v2 is not used. |
 | code2.cpp:128:9:128:9 | b | Variable b is not used. |
+| code2.cpp:194:6:194:16 | initialized | Variable initialized is not used. |
 | code.c:10:18:10:18 | y | Variable y is not used. |
 | code.c:11:18:11:18 | z | Variable z is not used. |
 | code.c:18:7:18:7 | x | Variable x is not used. |

cpp/ql/test/query-tests/Best Practices/Unused Entities/UnusedLocals/code2.cpp

@@ -181,3 +181,15 @@ void test_maybe_unused()
 {
 	[[maybe_unused]] int unused; // GOOD: explicitly marked as maybe_unused
 }
+
+int globalVar;
+
+int initialize()
+{
+	return ++globalVar;
+}
+
+void test_initializer_side_effect()
+{
+	int initialized = initialize(); // $ SPURIOUS: Alert // GOOD (initializer has a side effect)
+}

cpp/ql/test/query-tests/Best Practices/Unused Entities/UnusedStaticVariables/test.cpp

@@ -36,3 +36,16 @@ int initialize()
 }
 
 static int initialized = initialize(); // $ SPURIOUS: Alert // GOOD (initializer has a side effect)
+
+struct WithConstructor
+{
+	WithConstructor() { ++globalVar; }
+};
+
+struct WithDestructor
+{
+	~WithDestructor() { ++globalVar; }
+};
+
+static WithConstructor constructed; // GOOD (constructor has a side effect)
+static WithDestructor destructed; // GOOD (destructor has a side effect)