Reference RuleWithActions & Transaction object instead of copying values in RuleMessage

- Because the lifetime of the RuleMessage instances do not extend beyond
  the lifetime of the enclosing RuleWithActions & Transaction,
  RuleMessage can just reference it and simplify its definition.
- Additionally, make the references const to show that it doesn't modify it.
- Replace RuleMessage copy constructor with default implementations.
- Removed unused RuleMessage assignment operator (which cannot be implemented
  now that it has reference members).
- Removed constructor from RuleMessage pointer.
- Addressed Sonarcloud suggestions: Do not use the constructor's
  initializer list for data member "xxx". Use the in-class initializer
  instead.

headers/modsecurity/rule_with_actions.h

@@ -76,7 +76,7 @@ class RuleWithActions : public Rule {
     void performLogging(Transaction *trans,
         std::shared_ptr<RuleMessage> ruleMessage,
         bool lastLog = true,
-        bool chainedParentNull = false);
+        bool chainedParentNull = false) const;
 
     std::vector<actions::Action *> getActionsByName(const std::string& name,
         Transaction *t);