Define ordering on Rule instances and use on sets in RuleMatcher

Establishing reliable ordering fixes a test failure we're seeing on Alpine for
the signatures/tcp-end-of-match btest, since discrepancies in rule match
traversal could lead to discrepancies in corresponding event ordering.

src/Rule.h

@@ -59,6 +59,9 @@ public:
 
     void PrintDebug();
 
+    bool operator==(const Rule& other) { return strcmp(ID(), other.ID()) == 0; }
+    bool operator<(const Rule& other) { return strcmp(ID(), other.ID()) < 0; }
+
     static const char* TypeToString(Rule::PatternType type);
 
 private: