test, bench: make prevector and checkqueue swap member functions noexcept

Reason:
A swap must not fail; when a class has a swap member function, it should be declared noexcept.
https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#c84-a-swap-function-must-not-fail

src/test/prevector_tests.cpp

@@ -165,7 +165,8 @@ public:
         test();
     }
 
-    void swap() {
+    void swap() noexcept
+    {
         real_vector.swap(real_vector_alt);
         pre_vector.swap(pre_vector_alt);
         test();