Internals: Fix remaining cppcheck errors (#6319)

Fixed the non const-related issue and added suppressions for the const
ones. With that `make cppcheck` should be clean.

src/V3StatsReport.cpp

@@ -164,7 +164,7 @@ public:
 
     static double getStatSum(const string& name) {
         // O(n^2) if called a lot; present assumption is only a small call count
-        for (auto& itr : s_allStats) {
+        for (const V3Statistic& itr : s_allStats) {
             const V3Statistic* const repp = &itr;
             if (repp->name() == name) return repp->value();
         }