Avoid passing RuleMessage by std::shared_ptr and use a reference instead.

- Avoids copying std::shared_ptr when lifetime of the RuleMessage
  is controlled by the caller.
  - The RuleMessage instance is created in RuleWithActions::evaluate and
    then used to call the overloaded version of this method that is
    specialized by subclasses.
  - Once the call to the overloaded method returns, the std::shared_ptr
    is destroyed as it's not stored by any of the callers, so it can
    be replaced with a stack variable and avoid paying the cost of
    copying the std::shared_ptr (and its control block that is
    guaranteed to be thread-safe and thus is not a straightforward
    pointer copy)
- Introduced RuleMessage::reset because this is required by
  RuleWithActions::performLogging when it's not the 'last log', the rule
  has multimatch and it's to be logged.
  - The current version is creating allocating another instance of
    RuleMessage on the heap to copy the Rule & Transaction related state
    while all the other members in the RuleMessage are set to their
    default values.
  - The new version leverages the existent, unused and incomplete
    function 'clean' (renamed as 'reset') to do this on the current
    instance.
    - Notice that the current code preserves the value of m_saveMessage,
      so 'reset' provides an argument for the caller to control whether
      this member should be reinitialized.

headers/modsecurity/transaction.h

@@ -407,7 +407,7 @@ class Transaction : public TransactionAnchoredVariables, public TransactionSecMa
 #ifndef NO_LOGS
     void debug(int, const std::string &) const; // cppcheck-suppress functionStatic
 #endif
-    void serverLog(std::shared_ptr<RuleMessage> rm);
+    void serverLog(const RuleMessage &rm);
 
     int getRuleEngineState() const;