chore: import upstream snapshot with attribution

tests/fixtures/cpp_paired/Foo.cpp

@@ -0,0 +1,5 @@
+#include "Foo.h"
+
+void Foo::bar() {
+    value = 1;
+}

tests/fixtures/cpp_paired/Foo.h

@@ -0,0 +1,10 @@
+#ifndef FOO_H
+#define FOO_H
+
+class Foo {
+public:
+    void bar();
+    int value;
+};
+
+#endif

tests/fixtures/cpp_paired/Main.cpp

@@ -0,0 +1,7 @@
+#include "Foo.h"
+
+int main() {
+    Foo f;
+    f.bar();
+    return 0;
+}